Mitzi is a girl dog. She evidently likes Poncho, and does not blame him for the fact that he can not realize this, as he is neutered.
The two dogs grew up on the same street before Poncho and Chazz moved in with Carmen.
She briefly dated Bone Ripper, and went to the beach with him. Poncho and Boomer were also there.
They later met up again in the cafe. Poncho had completely forgotten about her, but she remembered him.
A few years later, they met again, also in the cafe. Poncho told Mitzi about many of his adventures. Mitzi gave Poncho her phone number. They talked on the phone for a while before Poncho eventually got the coarauge to ask her out.
They date was fine, until Poncho revealed that he was neutered. Gus then burst out of a bush and began to rant about how he "knew it". Mitzi didn't care though, and reffered to Poncho as "Sexy".
During her Spring Fever a few years later, word got around that she was into bad boys. During that time, she stayed with Poncho due to the fact that Boomer and other males surrounded her house. The next morning, Boomer accused Poncho of being "Mitzi's lucky Suitor" which he really is. Boomer then informed his friend that Bone Ripper was arriving to fight Poncho for Mitzi.
Before BR destroyed Poncho, Mitzi confessed her love for him. Bone Ripper then demanded that Mitzi and Poncho "prove" they were a legitimate couple. The two were able to convince him, and he left. Before Mitzi left Chazz's house, Poncho told her that he "had a fun time playing house".
- Mitzi is one of the only characters to break the fourth wall. When Gus was ranting about Poncho being neutered, she claimed she was spaayed (this has been disproved). She then picked a random direction, which happened to be the panel, and said "AND LET THIS BE A REMINDER TO EVERYONE TO SPAY AND NEUTER THIER PETS!"
- Mitzi is the only single most changed character in terms of appearance, having undergone three changes in appearance since she fist appeared.