This is like a Through the Looking Glass type idea. It's a children's movie/TV special that started w/ a girl in her bedroom, and her cat runs through her mirror and ends up in a magical land. The girl follows and I think has to deal w/ some evil queen.

Anyone know what I'm talking about? I don't think it was the Hugga Bunch because I don't remember puppets being involved.

The Hugga Bunch movie had berries or something and the evil queen would freeze people. Then she turned really old, at the end. Still not it?

I'm afraid its not Hugga Bunch, thanks though. There was definitely a pet cat. And the one I'm thinking of came out later than 1985. The more I think about it, I think it was a made for TV movie.

Could it have been adventures in wonderland, a TV series about alice in wonderland?

Did it have giant duck people?
If so, Magic in the Mirror... but there's no cat.
http://www.youtube.com/watch?v=wT_Ur0je7bM

The Alice in Adventures in Wonderland did have Dina the cat though.

I think you are talking about the Russian film Kingdom of Crooked Mirrors (Королевство кривых зеркал). I remember it from my childhood as well..
She eats the jam from the jar, brakes the jar, the mirror starts talking, the cats enters in the mirror, she follows and then there are two of them (the same girl) and they enter a magic land... Hope this helps.