Edit: I didn't even catch that you wrote Oolong... when was he a Z fighter? Him and Puar were friends of members, no?
Oolong was more relevant in dragonball. He was originally a villain that could shape shift (like the pig from monkey king legends). Goku exposes him and he started hanging out with them. Not really a Z fighter and even less so then Choutzu ... more like Puar who is just there but Puar is friends with Yamcha. He actually doesn’t even shape shift anymore when Z started up.