Look for the episode where Arnold holds his own magic show and he trys to make Helga disappear. Ok look for when Helga decides to play a trick and leaves the box from the back. As she opens the back door she walks off and does not close it and Arnold opens the box and the back door is in tact. Wouldn't you have seen right through the box if she had left the door open? Good trick.

And the turning the water to steam trick using the hot plate was just hilarious. lol