a whole other ball of wax

Something very different to, and often more difficult or complicated than, something else. It's one thing to babysit your friends' kids from time to time, but having your own children is a whole other ball of wax. I know you think you're some hotshot just because you worked in television once, but working on a film is a whole other ball of wax. A: "I've been here 10 years already, so I don't think becoming a manager will be a big transition." B: "Are you serious? No, managing employees is a whole other ball of wax."