There is a lot of humor to be had that is both appropriate and not G-rated. Humorous personal stories about awkward situations or odd situations, jokes about things that happened to people on the team (like the time susan brought the server down, or bob's ridiculous obsession with 80s pop), movie references, sexual innuendo (thats what s/he said is usually not sexist), political jokes, topical news jokes, and on and on.
I'm so sure you are going to come back with some "blah blah politically correct blah blah" disingenuity, I will adress it now: No, it's not all about PC and rules and whatnot, it's about genuine respect. Making comments and jokes centered on a person which aren't about that person, but about their membership in a class is generally not cool. It's called othering (and sometimes objectification). Othering is exclusionary, and a good joke for the target (but sometimes a good joke to the in-crowd, it solidifies their superiority!). Basically most jokes are OK, if they don't hinge on "and that's why that group is inferior and different from us".
I'm so sure you are going to come back with some "blah blah politically correct blah blah" disingenuity, I will adress it now: No, it's not all about PC and rules and whatnot, it's about genuine respect. Making comments and jokes centered on a person which aren't about that person, but about their membership in a class is generally not cool. It's called othering (and sometimes objectification). Othering is exclusionary, and a good joke for the target (but sometimes a good joke to the in-crowd, it solidifies their superiority!). Basically most jokes are OK, if they don't hinge on "and that's why that group is inferior and different from us".