Y is for Yo-Yo

 Chang Jie-Ru, otherwise known as Yo-Yo is a stretchy villain that was offered time in the Suicide Squad to "shave years off of his sentence." Unlike other elastic characters, he also has superhuman strength. During a mission to put down a riot at Belle Reve, he was eaten by King Shark and presumed dead. However, Yo-Yo survived and when Nanaue was knocked out, Yo-Yo was able to escape into the sewers. He was later reinstated into the team and even lead a mission to take out his sister, the villainous Red Orchid.

Because he survived inside King Shark's stomach I'm going to give him acid resistance. 

Code Name: Task Force X

Real Name: Chang Jie-Ru

Team Affiliations: Task Force X

Medium Humanoid, Neutral Evil

Armor Class: 14 (Natural Armor)

Hit Points: 65 (10d8+20)

Speed: 30 ft.

Challenge: 4 (1,100 XP)

Str 20 (+5) Dex 14 (+2) Con 14 (+2) Int 12 (+1) Wis 14 (+2) Cha 10 (+0)

Saving Throws: Str +8, Con +5

Skills: Athletics +8, Sleight of Hand +5, Stealth +5

Damage Resistances: Acid, Bludgeoning

Senses: passive Perception 11

Languages: Chinese, English 

Traits

Rubber Body: Yo-Yo can occupy another creature's space and vice versa. He can move through any opening large enough penny to fit through. He can stretch his limbs up to 15 ft.

Actions 

Actions

Multiattack: Yo-Yo makes three Unarmed attacks

Unarmed: Melee Weapon Attack +8 to hit, reach 15 ft., (one target) Hit 8 (1d8+5) bludgeoning or slashing damage.

Constrict: Melee Weapon Attack: +8 to hit, reach 15 ft., one target. Hit: 6 (1d8+2) bludgeoning damage. The target is grappled (escape DC 18). Until this grapple ends, the creature is restrained and the Yo-Yo can't constrict another target.

Bonus Actions

Size Alteration: Yo-Yo can change his size to small, medium, or large.