These cupcakes are older versions of the original Mr. Cupcake seen in Murray's Costume Manor, first appearing in Five Nights at Freddy's: Secret of the Mimic.

They act as antagonists, allerting Arnold's position to The Mimic, and they will also jumpscare him if he gets too close after they start alerting The Mimic.

These cupcakes have legs and wear a pair of roller skates similar to the original Chica costume.

Source: https://freddy-fazbears-pizza.fandom.com/wiki/Cupcake_Animatronics