I have seen several cases of people asking how to get Oswald to perform one of his various necessary jobs. (This is assuming you're playing solo.) There are quite a few spots that call for Oswald's cooperation--among them, when Mickey needs to be tossed higher than he can jump, etc. (There is, in fact, one film reel that can only be obtained by a cooperative toss--I think it's the one in the Mean St to OsTown projector.)
What I do is have my second controller handy. If Oswald won't do his thing (and he often won't--he's a little ADD that way, and likes to goof off,) you just push the split-screen/2 player button on Oswald's controller, make Oswald go where you need him, then set it down conveniently beside you. Grab your Mickey controller again (because you need it to control Mickey's jump,) then quickly push the "throw Mickey" button on the Oswald controller. Once you've got Mickey where you need him you can exit split-screen.