Yes...That happened. In Season 1. I'm sorry that I can't provide the exact episode, but you can search it in the "At the dance" videos uploades in Youtube. This can only have two explanations: Zoot and Janice were dancing tight or they were really in a relationship. After seeing this image...I would say number 2 is the correct.
This is the first time I draw Zoot in his muppet form. Sorry if it is a crap.