Tiny Tim is a cat with a broken leg that appears in A Special Sesame Street Christmas. Maria finds the cat in the alley behind 123 Sesame Street -- the injured cat had slipped on an icy fire escape. Maria dresses the cat up with a red ribbon, and puts a cast on its broken leg.
Maria introduces the cat to Leslie Uggams, and the pair decide to call it "Tiny Tim" in honor of the character Tiny Tim from A Christmas Carol.
They show the cat to Oscar who accuses it of breaking into his trash can on November 19th and stealing two fish.
In the end, Oscar has a change of heart and takes the kitten in, declaring "Are you people gonna stand around singing while that poor cat freezes? Hey, hand him up here."