Yeah, sometimes a funny image or idea will pop into my head and I'll laugh. It's not good when it happens in the middle of, say, when I'm supposed to be listening to someone, and looking like I'm laughing at what they're saying would be really bad.
As a kid (like just before school age) I'd sometimes find odd things inordinately funny. I'd have laughing spells that would go on and on, where I literally hurt afterward. I remember at least one parent being really weirded out by thate (and I was really oblivious to adults at that age, so that's saying something). I've always liked comedy, jokes, and joking around, and I've wondered if the laughter-part of my brain is mis-wired to be prone to little seizures or something. (I think of it as a good thing, though. A sense of humor is one of my few saving graces IRL.)