I myself tend to be a very humorous person, but I wouldn't make the first humorous remark right off the bat (maybe it's a personal preference, but whatever). I always wait and see how they act and if they're laughing and joking, I'm perfectly fine with laughing and joking back. If they're serious through the entire interview, you should probably be serious as well.
If you do joke, only joke about things that are very closely related to what's being talked about at that moment. Most importantly, try to be vague. Using specific names, companies, or brands may trigger the "Well, I like that [whatever it is]." Then you're in an awkward situation. Obviously the general rules of not being offensive, etc would always apply, no matter how comfortable you feel at the interview. Don't want them thinking you're racist or something.
One panel interview I attended was at a fire station, which we were unable to get into because it so happens that all the fire staff had gone out on calls and the building was locked. While we were standing outside, we made a lot of jokes about fire departments (in general). No specific names (of fire fighters) were mentioned, and it didn't focus on any specific fire department. Since they were already joking about fire departments in general, I felt perfectly comfortable joining in.
Remember that they are still people, and every person does things differently and takes what you say differently. Start off safe, learn what they think is acceptable, and go from there. Think of a potentially unwelcomed joke as a unnecessary risk that could jeopardize the interview.