The RainbowMaker 400 is a machine created by Dr. Weird just after creating the Rabbot. Weird presents this item in episode 2 and is inmediately stolen by the Leprechauns who enter by the Rabbot hole in the wall.
This thing is a towing device which uses a rainbow tractor beam to lift and bring other things. The Leprechauns have a tactic to mug people by using this to tow those who got lured by a "really stupid" chain e-mail (as described by Frylock), and after someone arrives at the park in hopes of obtaining gold, they're robbed by the Leprechauns.
This machine seems to work also in an opposite way, since Dr. Weird used it at the opening of the episode to throw away Steve instead of atracting him. It is possible that only Dr. Weird knows how to operate his machine to that point since noone else did.