The players are Mad Scientists creating fearsome monsters for the Evil Science Fair. Whoever completes the most monsters will win the prize. It takes various combinations of parts to create each monster, but be careful! Leaving unfinished work on the table could let someone else sneak in to finish it and claim the monster as their own. Just remember, only those who actually yell "Pull the Switch!" can lay claim to a monster.
According to the publisher the main changes were inclusion of rules for solitaire play, an altered the assortment of point cards in the game, and a couple of basic rule changes.