In your session zero you should talk about the level of humor you want in a game. For me, RPGs sing when there’s humor, it’s the spice that makes everything else fun and I’ll almost certainly try to add it as both a GM and a player. There are times where it doesn’t make sense, but I’ll always prefer times where it does. I think that’s why I enjoy Dungeon Crawl Classics so much. It’s a game that doesn’t take itself too seriously and generates humorous situations. For instance, I was playing in a game of Mutant Crawl Classics—it’s post-apocalyptic spinoff—and we were told to look for the “Cou spital”. We wandered around a bit and found a “black lake” in front of a building. We touched our toes to the black lake and it wasn’t water or even wet, it was solid. My character gingerly took a step on it and it held him, but this sorcery was not of this world! I ran at full sprint across this black sea to get to the building on the other side, jumping on these regularly spaced white stripes to make it to the “Cou spital” safely!
Turns out I was jumping through a parking lot, going from line to line to make it to the “County Hospital”.