Which actor played the character Nick Charles in the "Thin Man" films of the '30s and '40s?

Love Thin Man

Player #11743474, and Asta, their dog.

I don't think I ever saw any of the films. They had a TV series that ran from 1957-59, starring Peter Lawford and Phyllis Kirk as Nick & Nora - and Asta as Asta, of course. It's one of the earliest TV shows I can remember seeing.

I love thTmovie. it's cute and well acted, the dog Astor was even involved in the mysteries. I think k there were more than one movie.

But who played Asta?