For anyone having trouble, here's a walkthrough of how you can beat each level:
1: Click the light red button on the TV.
2: Click the left guy's eyes.
3: Click the triangle on the green door, then click the door itself.
4: Click the guy five times, then click the pipe segments to make one connected run.
5: Click the group of three people, then click the leaves of any one of them.
6: Click the zipper pull right behind the bull's horns.
7: Click the wand when you're a human.
8: Click the car 18 times, then wait.
9: Click the guy 19 times.
10: Click the word "Trollface" 10 times.
11: Click the small black "minimize" button on the "lifelines" window in the upper-right twice, then click the "win" button.
12: Drag the piece of candy through the maze to the trollface, drag it up and outside of the puzzle, then click on the "next level" button.
13: Click the green triangle to move the car down, click the triangle to move the car up (after you pass the first black box), then click on one of the two black boxes as they approach the car.
14: Click on the boulder right before it hits the man.
15: Click the green button on the left 99 times, then click the green button on the right once.
16: Let the walls close in on the man, and when the blades almost hit him, click the small button on the upper-right corner of the right wall.
17: Click the nine trollfaces, then click the trollface on the "level failed!" window next to the "restart" button.
18: Click the "jump" button so you jump over the first two spike traps, but walk over the third.
19: Click the following notes: third from the left, leftmost, fourth from the left, second from the left, then click on the man.
20: Click the wires, then click the light red button on the TV.
Hope that helps anyone that was stuck.