Last updated: June 5, 2026·🔄 Guide reviewed and refreshed ahead of Halloween 2026.· By Seckin Peker

Halloween Costume Guide

Blueberry Sans From Undertale Halloween Costume Guide

Energetic. Optimistic. Technically not in any official game, which has not slowed him down at all.
Cute Mask
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Quick Answer: Blueberry Sans is a grey and turquoise skeleton build where the mask and the turquoise accents together create the character.
  • Sans Mask (essential)
  • Turquoise Scarf (essential)
  • Grey T-Shirt over Turquoise T-Shirt
  • Grey Shorts
  • Turquoise Satin Gloves and Turquoise Shoe Cover

Blueberry Sans is a fanon character from the Undertale fan community, specifically a fan-made interpretation of Underswap Sans from the Underswap AU. He is not in any official Undertale game by Toby Fox. What he is, however, is extremely enthusiastic about everything, fully committed to becoming a royal guard, and very into tacos. His personality is essentially Papyrus’s unbounded ambition placed inside a smaller skeleton wearing blue, and the fandom has embraced this fully for over a decade.

Items Total7 Items
DifficultyEasy
VibeEnthusiastic Fanon Skeleton Hero
Cost$50–$130

Blueberry Sans Halloween Costume Items

Blueberry Sans Undertale Halloween costume guide 7 items

Blueberry Sans Costume Items

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Blueberry Sans Underswap Undertale AU Sans
  • 1 Grey T-ShirtThe outer shirt layer, worn over the turquoise t-shirt (item 4). It should sit comfortably loose enough that the turquoise collar and lower hem of the shirt beneath it show clearly. The grey is the base tone of Blueberry’s look, with the turquoise accent breaking through at the edges. A plain, unfussy grey tee is exactly right.
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  • 2 Grey ShortsSimple grey shorts to complete the lower half. Comfortable, plain, and practical for an evening of enthusiastically explaining to people that you are going to be a royal guard. Check your closet first for any plain grey shorts before ordering.
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  • 3 Sans Mask (essential)The skeleton mask is the item that makes this a Sans character rather than a person in grey and blue. Without it, the rest of the costume is just casual clothing with turquoise accessories. Confirm the mask fits comfortably and allows clear vision before the event. A skeleton mask that restricts breathing or sight becomes a problem quickly in a crowded venue.
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  • 4 Turquoise T-ShirtThis goes on FIRST, under the grey t-shirt (item 1). The turquoise should be visible at the collar and the lower hem where the grey shirt ends, providing the signature blue-teal accent visible in Blueberry Sans fan art. Get one slightly longer than the grey shirt to ensure it shows at the bottom.
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  • 5 Turquoise Scarf (essential)The most visible turquoise accent in the costume and the one that Undertale AU fans will look for first. In fan art and community depictions of Blueberry, the blue-turquoise color runs consistently through his look, and the scarf is the clearest reference point. Wear it loosely around the neck with the ends visible at the front.
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  • 6 Turquoise Satin GlovesBlue or teal gloves are a consistently appearing accessory in Blueberry Sans fan depictions, added to the base Underswap Sans design by fan artists over time. They add to the color cohesion of the build and add a slightly theatrical quality to the look, which is accurate to the character’s energy.
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  • 7 Turquoise Shoe CoverThe turquoise shoe covers complete the all-over blue accent look at the feet. They go over whatever footwear you are already wearing and tie the color palette together from top to bottom. Confirm they fit securely and will not slip during a full evening before the event.
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Blueberry Sans costume reference turquoise skeleton Undertale AU

How to Style the Blueberry Sans Halloween Costume

The layering order matters here. Turquoise t-shirt first, grey t-shirt over it, with the turquoise showing at the collar and the hem. Everything else adds the accent color outward from there: scarf at the neck, gloves on the hands, shoe covers at the feet. The mask goes on last. The full effect is grey base with consistent blue-turquoise running through the edges, which is the visual signature that Undertale AU fans will recognize. Test the mask at home before the event to confirm it sits correctly with the scarf.

Blueberry Sans is best understood as Papyrus’s personality crammed into a shorter skeleton with different food preferences. He is absolutely certain he will become a royal guard. He greets strangers with complete trust. He says “Mweh Heh Heh!” and means it as an expression of genuine enthusiasm rather than theatrical menace. He would like you to know that tacos are better than spaghetti, and he has a complete argument for this position that he is prepared to deliver at any moment.

Layer the shirts in the right order

The turquoise t-shirt needs to go on before the grey one, and it needs to be long enough to show beneath the grey hem. If you buy both items, check the length comparison before the event. If the turquoise shirt is the same length as the grey one, the lower accent will not show, and you lose one of the three turquoise reference points (collar, hem, accessories) that build the character. Pulling the grey shirt up slightly or tucking it unevenly solves this if the shirts are the same length.

Play the enthusiasm fully

Blueberry Sans is one of the few fanon characters where the entire personality is just enthusiasm with no counterweight. He is not secretly sad. He is not ironic. He has boundless energy, a strong sense of justice, and complete confidence that his hero training is going well. At a party full of Undertale fans, saying “Mweh Heh Heh!” with absolute commitment and then immediately explaining your royal guard qualifications is the correct approach. The more serious you play the enthusiasm, the funnier it gets.

Blueberry Sans Group Halloween Costume Ideas

Couples Idea

Blueberry Sans & Stretch (Underswap Papyrus)

Might work, but this pairing requires both people to be deeply in the Undertale AU community. Stretch (the Underswap Papyrus) is Blueberry’s laid-back, unimpressed counterpart, and the contrast between Blueberry’s extreme enthusiasm and Stretch’s general calm is one of the most popular dynamics in fan content around these characters. Stretch has no CostumeRealm guide, so that costume is a full scratch build. At a convention with a strong Undertale AU crowd, this pairing lands immediately.

Blueberry Sans Stretch

Duo Idea

Blueberry Sans & Papyrus (Undertale)

Strong duo for Undertale fans. Pairing the fanon Blueberry Sans with canonical Papyrus creates a visually coherent skeleton duo that covers both the original game and the AU community in one group. Both characters share theatrical enthusiasm and hero ambitions, and the visual contrast between blue-turquoise and Papyrus’s red-and-white works well. Papyrus has a CostumeRealm guide. At a gaming event, both characters will be recognized, though by slightly different audiences.

Blueberry Sans Papyrus

Group Idea: Undertale Skeleton Family

Blueberry Sans, Papyrus, Sans (Classic), Ink Sans

Might work, but this group is built for an audience that knows Undertale and its AU community deeply. Ink Sans has a CostumeRealm guide. Classic Sans and Papyrus require scratch builds within the group. The visual range of skeleton designs across these characters is actually strong: grey and turquoise, red-and-white, grey hoodie, and Ink Sans’s distinctive paint-splattered look. At a convention with an active Undertale fan presence, this group will stop people in their tracks. At any other event, it will stop very few.

Blueberry Sans Papyrus Sans (Classic) Ink Sans

Group Idea: Colorful Animated Skeleton Characters

Blueberry Sans, Papyrus, Jack Skellington, Brook, Oogie Boogie

Strong group with broad visual appeal at any Halloween event. Five skeleton characters with completely different aesthetics and franchise origins: blue-turquoise fanon skeleton, red-and-white theatrical skeleton, tall gothic nightmare skeleton, top hat jazz skeleton, and burlap sack villain. Jack Skellington and Oogie Boogie carry the widest Halloween recognition. Brook requires One Piece knowledge. Papyrus and Blueberry Sans bring the gaming crowd. Jack Skellington and Oogie Boogie have CostumeRealm guides.

Blueberry Sans Papyrus Jack Skellington Brook Oogie Boogie
Blueberry Sans Undertale AU group costume reference

Blueberry Sans Halloween Costume DIY Tips

Building the Costume

Seven items, straightforward to source, with one important layering detail that can be missed if you are not paying attention to item 4.

  • Turquoise t-shirt (item 4): goes on FIRST. It should be slightly longer than the grey t-shirt (item 1) to show beneath the hem.
  • Grey t-shirt: goes over the turquoise. Turquoise should show at both the collar and the bottom hem.
  • Grey shorts: simple, no substitutions needed. Check your closet first.
  • Sans mask: test comfort before the event. Vision and breathing should be unaffected.
  • Turquoise scarf: the most visible accent. Wear it loosely, not knotted tightly.
  • Turquoise gloves: confirm they go on and off easily; you may want to remove them at points during the evening.
  • Turquoise shoe covers: fit check before the event. They should sit securely without slipping.

Playing Blueberry Sans at the Party

Blueberry Sans is one of the purest expressions of boundless enthusiasm in the Undertale fandom. He has no hidden depths of sadness or irony. He is genuinely, completely enthusiastic about everything, and he wants you to know about it.

  • “Mweh Heh Heh!” Deliver with complete commitment. Not as a joke. As an expression of genuine feeling. This is the difference between playing the character and playing at the character.
  • He is convinced he is going to be a royal guard. If anyone questions this, he has responses prepared.
  • His favorite food is tacos. If there are tacos at the event, this is your moment. Papyrus likes spaghetti. You like tacos. This is character development.
  • Blueberry is technically shorter than regular Sans in fan depictions. Act accordingly small, which for a skeleton involves bending the knees slightly and having opinions that are very large relative to your height.
  • He is not in any official Undertale game. He does not know this. Do not tell him.

Blueberry Sans Halloween Costume: FAQ

Layer the turquoise t-shirt under the grey t-shirt so the turquoise shows at the collar and edges. Add the grey shorts, turquoise scarf, turquoise satin gloves, and turquoise shoe covers. The Sans mask goes on last. The combination of grey with turquoise accents is the visual signature that separates Blueberry Sans from classic grey Sans.

Niche but solid within the right crowd. Undertale’s fandom remains active and the AU community is large enough that at a gaming or anime convention you will find people who recognize Blueberry Sans immediately. At a general Halloween party, the costume reads as a blue skeleton, which is still a striking look, but the specific character will need introduction.

His catchphrase is “Mweh Heh Heh!”, a swap on Papyrus’s “Nyeh Heh Heh!” from the original Undertale game, reflecting his Papyrus-like personality in fanon. It is one of the most consistent details across all fan interpretations of the character and one of the fastest ways to signal who you are at a party full of Undertale fans. Deliver it with complete sincerity. That is the correct approach.

No. Blueberry Sans is a fanon character, not part of official Undertale by Toby Fox and not part of the original Underswap AU concept either. He is a fan-created, exaggerated interpretation of Underswap Sans that became popular through early Tumblr fan art communities. The original Underswap AU creator actually distanced themselves from the Blueberry interpretation, which has not slowed Blueberry down at all.

Classic Sans from Undertale is laid-back, pun-obsessed, and famously lazy. Blueberry Sans is the personality opposite: energetic, enthusiastic, obsessed with becoming a royal guard, and completely convinced he is going to be a hero. He also prefers tacos over ketchup, which is a significant lifestyle difference.

The Sans mask and the turquoise scarf do the most recognition work. The mask identifies this as a skeleton character. The turquoise accents, especially the scarf and gloves, identify this as the blue variant associated with Blueberry Sans. The turquoise t-shirt worn under the grey adds the color detail at the collar and hem that completes the layered look.

In the Underswap AU, the skeleton brothers have swapped roles: Sans (Blueberry) has the energetic, ambitious personality that Papyrus has in the original Undertale, while the Underswap Papyrus (sometimes called Stretch) is more laid-back. The sibling dynamic is one of the most popular elements of fan content around these characters, with Blueberry’s boundless enthusiasm playing against his brother’s calmer approach.