Telephone is an anthropomorphic telephone.
Telephone is an anthropomorphic telephone originating from a surreal world behind the mirror in Mickey Mouse's house. Mickey once traveled to that world, where he met Telephone, who started out making fun of Mickey but eventually befriended them. Later, Mickey left the world, and seemingly decided that the adventure must have been a dream due to its fantastical nature. Being so forgotten, the Mirror-World's inhabitants ended up in Wasteland, including Telephone
In 2010, Telephone got into an argument with Gremlin Prescott, and stole his wrench. Gremlin Prescott dismantled Telephone to get it back, scattering their pieces around Ostown. Gremlin Gus found these pieces, and reassembled Telephone, after which they lived in Ostown's replica of Mickey Mouse's house, and occasionally spoke with Mickey himself.
Behind the scenes
Telephone first appeared in the cartoon Thru the Mirror in 1936. It later reappeared in the Epic Mickey series.
In the original short and Epic Mickey, Telephone is depicted as male, but the character is referred to as female (and voiced by a woman) in Epic Mickey 2: The Power of Two. Whether this was a goof, a deliberate retcon, or is to be taken as Telephone genuinely switching genders in-between games somehow, remains unknown.