Pet Shop appears as a playable character and was only available in the second version of the game.
All of Pet Shop's moves are based on his ability to create ice, such as throwing Ice Stakes, trapping the enemy on the ground with ice or anything related to icicle attacks. His first special move shoots several ice stakes with great speed as a projectile attack. His second special move creates a giant ice block that comes from above the screen (the same move he used to kill the agent in front of DIO's mansion). His last special move sends Pet Shop to the back of the screen from where he shoots even more ice stakes at the opponent. This, however, only works as a grab special move.
Pet Shop is widely considered the most powerful character in the game, with incredibly strong special control from his many projectiles and unblockable setups stemming from his overhanging icicle attack. Playing Pet Shop is generally considered "poor taste" and he's typically soft-banned in most Tournament settings.
If hit by Alessi's Stand attack, Pet Shop turns into an egg but still can use his Stand to make small icicles, possibly implying that Pet Shop was born with his Stand ability.
His ending on Arcade Mode portrays a hypothetical situation in which Pet Shop manages to kill all the main heroes. Pet Shop continues to act as the guardian of DIO's Mansion, as the text says "And Pet Shop never allowed anyone to come near the Mansion, anyone...".