At some point there happens to be a Thing Three and Thing Four.
In the film, Thing One is played Danielle Chuchran and Taylor Rice, and Thing Two was played by Brittany Oaks and Talia-Lynn Prairie but Dan Castellaneta provided the voices for both of the two Things.
In The Cat in the Hat (1971 cartoon), Thing 1 was voiced by Thurl Ravenscroft and Thing 2 was voiced by Lewis Morford.
The Things wear red jumpsuits with the logos 1 and 2, and they have blue afro hair in their other appearances. In the Learning Library, they are wearing blue jumpsuits and thier afro hair is blonde.