...a condom.
"Ya know, Zack, I'm tired of my brother screwing with me. And you know while they say turnabout is fair play, I really am not too keen on sloppy seconds."
"Huh? Oooahh!" Zack's mouth stuck in an o-form and his body changed to a shiny red latex. He started to lurch forward fearing that he was about to become a blow up doll too. He wasn't so lucky.
Jeff calmly strode over to the red latex disk and picked it up, in the rubber tip he could make out the imprint of Zack's face moving. This was too rich. So Zack could not only sense Jeff and what was happening to him, but he could react and move in a limited fashion. The condom unrolled itself attempting to escape Jeff's grasped. His index finger and thumb held firm, and his cock rose to half staff. He rolled the rubber over his rod, and gently tapped Zack on the head, and then he walked over to Ken.
"Hey, bro, you screwed with me. Now it's my turn. Bad news, bro, Zack here set your duration for two whole months. I was going to change you into a dog, but the menu on Chronivac said that program would activate in two months." He shrugs, and flips the Ken doll over, and fills the Zack the condom with his cum. Then with slick sweat covering Jeff's body he dozes off on top of the inflatable man. There's a hissing sound as one of seams begins to split. When Jeff awakes he's horrified to find his brother completely deflated. He picks up the flattened rubberman, and tries to find the valve to reinflate him.