I saw your post at the Steam forum. Do I understand correctly that you have a one-button mouse and you use control-click to simulate right-click? While that's the way it's supposed to work in the Mac OS and most regular programs, it's not necessarily going to work in games. I don't know whether Sam & Max is designed to support that or not.
Anyway, I can't try to reproduce or help with your problem since I haven't used an Apple mouse, or any one-button mouse, with my Macs since the early nineties.
If you're serious about playing games on your Mac, you're going to need the latest Apple mouse or a third-party two-button (at least) mouse.