Combo king: before you enter the mojo room there is a cage hanging on your right side with a Shellephant in it. If you have an ee-lectric continuasly use it's regular attack on the shellephant. After some time you will complete the combo king "challenge"

Minion Master: You just have to defeat every minion you see and, while you are defeating Uka-Uka, you will complete this "challenge"

Spybots: The spybots are the easiest part. You don't even have to look for them. As you progress through this level you will easily find all of them.

Hope this helps ;)