"We should make sure our costumes fit." You say. Jack nods and gets up. The two of you go to your respective rooms and put on the costume.
As you pull the silky costume up your legs, you picture Jack in the other room taking off his shirt. You pull the upper half on and think of Jack's pecs being revealed as he unbuttons his shirt. When you put the gloves on, you think in your mind's eye about Jack's butt as he bends over to pull off his socks. As you pull on the skintight mask, you can almost see Jack's naked penis flopping out as he pulls off his briefs.
Good and hard now, you go over to the mirror to take a look at yourself You're a little confused at first, wondering who replaced your mirror with a cleverly disguised high def TV display showing ...
You're shorter, about the size of a 15 year old, and your face and body proportions have changed to suit. The only thing distinctly adult about you is the penis, rock hard and waving after all the picturing you did of Jack.
"Whoa." You whisper to yourself, and see the costume's mouth move very realistically. You shake your head. Far too realistically! You lean in, and touch it with one outstretched hand. You see your hand - no way is this a costume! You've turned into a rabbit boy!