Yes, CARTOON is a Scrabble word!

Letter values in Scrabble US: C 3, A 1, R 1, T 1, O 1, O 1, N 1.

Is it a valid word?

CARTOON is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a humorous or satirical drawing published in a newspaper or magazine
a film made by photographing a series of cartoon drawings to give the illusion of movement when projected in rapid sequence

Also: animated cartoon.