Monstro and Bio Vipers, large monster figures which were supposedly the results of Cobra's biological experiments on their own troops, were a striking departure from typical GI Joe figures. As well as being treated with perfume to give them a 'monster smell', these bulky figures each had their own gimmick; Monstro Viper could lob a Play-Doh 'gut bomb' shaped in a hollow chest cavity via a spring-loaded arm. Bio Viper had flexible tentacles which could be operated via a lever on the figure's back. This caused thin nylon wire strung through the tentacles to tighten, closing around any unsuspecting Joe figure who strayed too close.