Button names to those that don't know:

LP = Light Punch (X on 360 or square on dualshock)
MP = Medium Punch (Y on 360 or triangle on dualshock)
HP = Heavy Punch (RB on 360 or R1 on dualshock)

LB or L1 can be held down to hold all three punches at once.

LK = Light Kick (A on 360 or X on dualshock)
MK = Medium Kick (B on 360 or circle on dualshock)
Up = Hold up on the d-pad or analog stick.

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To put it quite short, you need to hold all three punch buttons, LK, and Up while the stage is loading to access each costume change. The only exception to this is Urien's thong which has a different input.

To go into Urien's classic SFIII thong, hold LP, HP, and MK while the stage is loading. If done correctly, Urien's usual intro will be different and he'll burn off his clothes to reveal his glorious man-thong.

Keep in mind that this button input is different from all of the other ones.


https://www.youtube.com/watch?v=YrzFzOlLqWE

Akuma can go shirtless by holding LP, MP, HP, LK, and Up while the stage is loading. Only works on his classic costume.





https://www.youtube.com/watch?v=2Q6pP7Ib9yE

Swimming time, better take off some clothes before going in! All of the female swimsuit outfits have an article of clothing that can be removed in some way.

For all of the female swim outfits, hold: all three punch buttons, LK, and Up while the stage is loading. The following changes will be made once doing so:

• Cammy's swimsuit loses parts of the armor
  
• Chun-Li's swimsuit loses the skirt
  
• Ibuki's swimsuit loses the scarf
  
• Karin's swimsuit loses the hat and shades
  
• Laura's swimsuit loses the jersey
  
• R. Mika's swimsuit loses the hoodie

https://www.youtube.com/watch?v=KFM8RZ-oHpo

The now unobtainable CPT costumes can be altered as well. Like before, hold all of the punch buttons, LK, and Up while the match is loading. The differences in doing this are:

• Cammy loses the scarf
  
• Chun-Li loses the scarf
  
• Necalli loses the vest

https://www.youtube.com/watch?v=0Eo-CS_1D90

Have you ever seen someone dressed like a hipster and said to yourself, "I want to get rid of those clothes for good?" With this trick, you can sort of remedy the issue.

Ryu and Chun-Li's Red Bull outfits can be adjusted as well by holding all three punch buttons, LK, and Up before the match starts. The changes are:

• Chun-Li loses the furry jacket
  
• Hipster Ryu loses the jacket

Things have been getting so spooky that various clothing accessories have started to disappear! Legend has it that holding LP, MP, HP, LK, and Up while the match is loading causes this to happen. The changes in doing this are:

• Alex's demon costume loses the horns on the shoulders
  
• Cammy's corpse bride costume loses the bridal headpiece and the roses on her wrists
  
• Juri's devil costume loses the horns on the head
  
• Nash's Frankenstein costume loses the shirt
  
• Necalli's werewolf costume loses the vest
  
• Ryu's samurai costume loses the helmet
  
• Vega's costume loses the cape

https://www.youtube.com/watch?v=3j89lKYRVb8&t=110s

Seems like the cold doesn't bother these fighters, so they'll have no trouble taking some clothing off during winter.

Like every other non-Urien costume, hold LP, MP, HP, LK, and Up while the stage is loading. The changes to the costumes are:

• Juri's Christmas outfit loses the scarf
  
• Karin's santa outfit loses the hoodie
  
• Ken's cowboy Christmas outfit loses the shades and adds antlers to the hat.
  
• Laura's skimpy Christmas outfit loses the belt and earns her a spot on Santa's naughty list
  
• R. Mika's santa outfit loses the jacket
  
• Zangief's bear outfit loses the bear head

https://www.youtube.com/watch?v=LGa_ugQdHyY

Kolin's optical vision can be improved by doing the general costume code (3 punch buttons + light kick + hold up) while the level is loading. Only works for her nostalgia costume.
















[Pic from /u/DoggiePeak61]

Like every other non-Urien alt costume, hold down 3P + LK + up while the stage is loading. Here are the changes:

• Chun-Li's costume loses the braids and now has loose hair.
  
• Juri's costume loses the black jacket.
  
• Ryu's costume loses the jacket.

Use the famous 3 punch + LK + up button combo on the loading screen to gain acess to these new costume features:

• Alex's firefighter outfit loses the hat and has a red bandana instead.
  
• Chun-Li's business outfit loses the jacket.
  
• R. Mika's cheerleader outfit loses the pom poms.

• Ibuki's outfit loses the scarf.
  
• Mika's outfit loses the braids and her hair now goes behind her.
  
• Nash's outfit opens up the jacket.

• Alex's outfit gains his sweet bomber jacket.
  
• Ibuki's outfit loses the scarf.
  
• Juri's outfit gains a little jacket.

(Just added to the game, will update in a bit)

• Bison's outfit loses the cape.

• Bison's devil costume loses the cape.

I hope this guide helped in all of your SFV costume changing needs. Credits to Eventhubs for using some of their pics, as well as the videos used.

If there are any errors/new additions, please say so in the comments.