Hey Bombjack! :D
I think IIRC in my law class- companies can't really own a "design" or some sort. Like- for example, a Female Sniper character can be made into thousands of different games- and it would be unfair to sew X or Y company. So- I think putting a character with red clothes in a blue jumpsuit us completely fine as long as you don't put it around your brand?
I think it really depends on your intent. If you promote your game using a character that seems as iconic as Mario, for example- that's definitely something that might confuse people with your game being related or affiliated with Nintendo- which is bad. I'm sure there are ways to get around this to get the cultural references- but I believe it really depends on how well you execute it.
"Time Traveling Warrior", "Jumping Plumber". Something as general as that? You can't be sued- and I'm sure players will get the reference you're trying to pull out from.