What is the tom and Jerry episode where chalkboard comes to life?

You're likely thinking of the episode "The Cat and the Fiddle" (1947).

In this classic episode, Tom tries to play a fiddle, but Jerry keeps interrupting him. Frustrated, Tom decides to write "No More Jerry" on a chalkboard. However, the chalk letters suddenly come to life, and they start chasing Tom around the house.

This episode is famous for its hilarious use of animation and the comedic absurdity of the chalkboard coming to life.