When the robots rip open a door to an alternate dimension, a mysterious small purple alien blob creature from another dimension falls through into Tails hands and Sonic lets him keep it. Simple? Wrong! The one problem is, the alien will only eat. . . Guess . . . Yep, chilidogs! And if it doesn't get them it grows into a huge alien, goes ballistic, and sucks everything up in sight. The alien - now named Goopster, is in constant danger as the robots would find it more useful as a weapon, and are constantly try to capture it. However, Dr. Robotnik steps in, kidnaps it and Sonic and Tails must go to rescue it! But things get really haywire when Robotnik angers the alien and it sucks up Sonic and Tails instead! The heroes eventually trick the robots into sending it home to its parents as things return back to abnormal.