Poochie was first referred to by name on December 17, 1972 and made her only appearance in Peanuts in the Sunday strip from January 7, 1973. It is revealed in that series that she was a girl who lived in the neighborhood some years earlier but moved away and that Snoopy bears a grudge against her. In the Sunday strip from December 31, 1972, Snoopy explains that he does not like Poochie because of an incident when he was a puppy.
He's Your Dog, Charlie Brown! Snoopy's driving everyone crazy! So Charlie Brown arranges for him to return to the Daisy Hill Puppy Farm for a little obedience training. On the way, he makes a stop at Peppermint Patty's house, and decides to stay there.