Dave's Disguises is a location in the city called Shredderville, previously known as New York City.
When the Turtles first arrives in the sewers of Shredderville and go topside, they realize quickly that they are no longer in their own world. The streets are a mess and the buildings are falling apart. To make matters worse, a loudspeaker repeats the words "All mutants are to be hunted down. Mutants are your enemies."
Leonardo laments the fact that they do not have any disguises, but Donatello spots a store called Dave's Disguises. The store is in as much disrepair as the rest of the city, its front door hanging off its hinges, and the front window glass broken.
The proprietor of the store, Dave, is watching television and ignores them while the Turtles explore. Donatello tries on an Australian type hat and speaks with an accent, but Raphael switches the hat out for mouse ears.
When Michelangelo goes to pay for four costumes, Dave becomes incensed, accusing them of trying to give him phony money. He claims that it is as worthless as they are, because they are mutants. The only valid money in Shredderville has a picture of Shredder on it.
Dave chases them out of the store. Neither Dave nor Dave's Disguises is seen again, as the entire Shredderville visit proves to have been a shared dream by all four of the turtles.