The Bosses in the game are:
Hungover - NONE
Windy - If you consider the bull to be the boss. If you do then I'll tell you how to Kill him. First, run up the barrel(to do that past the platforms that have rolling poo) Once you're on top of the barrel, walk forward to the tap. Once on the tap, run clockwise, and prune juice should come out of the tap. After doing so, make the bull ramb into the target. After that, Make the bull ramb the new target, then when he's STUCK, jump on him, and you should be able to ride him. aline yourself with the bull and the cow, then RAMB THE FRICKIN COW! (press Z) After that, ramb it again when it's on the sewage pipe. It will then explode and another target will appear. Do this 3x, and you'll defeat him. Cows hits for it to drink the prune juice are: 1st cow - once, 2nd cow - twice, 3rd cow - trice.
Barn Boys - Haybot. Strategy - Jump on Franky and start hopping away. Lure Haybot to use one of his Suzie 9mm on the pipes. Once he does that, water will start pouring out. Hide behind the pipe that has water coming out, until you see Haybot's sparks fly like crazy. He'll then go to the middle and start spinning. Run up to him and when you see the red button, jump(A) and punch it(B). You can only punch it if you see the context sensitive thing. Do this 3x. I won't tell you how to get out of there, because I had to suffer like you did.
Bats Tower - Brass Monkey. This is an extremely easy boss. Run and jump on one of those platforms with a lever over it. Once on it, wait till Brass Monkey jumps onto the sewage pipe thingy, once he does, crouch jump(Z + A) you will pull the lever. After doing that, run off of the platform and run up to his balls, then when the context sensitive thing comes on, press B and you thwack his balls with two bricks. Do this 4x.
Sloprano - The Great Mighty Poo. He's also an easy boss. When he throws his poo at you, dodge it, and keep on dodging them until he starts to sing. Then, you run up to the context sensitive thing and pull out toilet paper. Throw it in his mouth. Do this 3x. Number of times you have to throw it in his mouth for each context sensitive. 1st - once, 2nd - twice, 3rd - trice.
Uga Buga - Buga The Knut. To Embarrass him, run up to his "cloth" when he's about to swing at you and bite! After doing so, run behind him and bite his buttcheck off. Do this 3x. This may look simple, but it isn't.
Spooky - NONE
It's War - The Experiment. This is VERY VERY easy. First shoot off both of his mini-guns. Then shoot the little girl. He'll run to the girl and when the little hatch behind him opens, shoot it. do this 3x. Weapons that he/she has: 1st - mini-guns, 2nd - lazers, 3rd - Mark 2's. Each can be shot off by 1 hit.
Heist - Xenomorph. THE HARDEST BOSS EVER!!! But he can be easily destroyed..if you have talent. First walk up to him. If he turns a bit to the left (on you) then he gonna swing his tail. So, jump(A). If he moves his head back, He gonna try to bite you. If he tries to bit you, press (Z) which is block. (NOTE: BLOCK DOESN'T WORK ON THE TAIL SWING) Then he'll start shaking his head. Use your cool 3-5 hit combo on him (keep on pressing B) and he'll be knocked down when you uppercut him. Quickly run behind him, and you should automatically grab his tail. start swing him by turning your control stick eith clockwise or counterclockwise. When the sparks stop, get ready to throw him out the door(B). But you HAVE TO throw him OUT the door. NOT the wall. Do this 3x. When the Endcut sceen comes, and the Xenomorph is stuck while jumpng towards you, DON'T restart your N64. It's apart of the End Cutsceen.
Well, that's all of the bosses. I'm tired from typing so much so I'm gonna rest now.