You print "BATMAN", then hold the jockstrap out and smile. You step into the jockstrap. It seems suddenly snugger than before. It seems to be getting stiffer, and so are you. You look more ripped already. You start to grin, but the muscles don't seem to work. You touch your face it feels rubbery to the touch. Your body seems to be losing definition now, you're shorter than before. How is that possible, does Batman wear lifts? Yours skin starts to get red, like a rash is breaking out, then you notice that the magic jockstrap has become a black rubber jockstrap with a bat shaped cut out just below the waist band over the pouch. It's too stiff and small a space for a fly, perhaps its ventilation or just styling.
You try to pull off the magic jockstrap, but it has fused to your skin. It's part of you now. The marker! If you can remove the ink, you can stop this transformation. There is some paint remover in the garage. You start to run down the hall, but when you reach the stairs your legs no longer will bend. You fall headlong down the stairs, bouncing and shrinking all the way down. You look up at the mirrored wall at the base of the stairs. All you see is a black jockstrap with a red bat logo. Oh, no, you concentrate trying to feel your legs and arms, and realize that you are now a bright red rubber cup. The world shifts and distorts, a magic worm hole transports you into a dark place. You smell rubber and sweat and electronics. A mobile rings.
"Yes, Bruce? The Royal Flush Gang, again? Right, Batman will be right on it."
The dark place is suddenly illuminated as the zipper is opened on the back pack. You recognize the pointed ears of Batman's costume looming over you. A hand reaches in, and lifts you out. Of course, he would put the jockstrap on first. Then you see his face.
"WHOA! Terry McGinnis is Batman? No way!" you think.
In minutes, Terry has changed into the cybernetically enhanced Batsuit. For a moment he blinks, the world seems dark, damp, and smells like a locker room.
"Terry are you there! Terry!" a voice shouts out of the built in transmitter in the Batsuit's head.
"Huh? Oh, yeah, here I am, Mr. Wayne," Terry says groggily, "Jeez, I really need to give this suit a good cleaning, it smells like my dirty underwear." Terry yawns loudly.
"You sure you're okay, Terry? I've been trying to raise you for over 5 minutes. You said the suit smelled funky, check your respiration system, perhaps there are traces of Joker gas or--wait, I'll run a diagnostic. No, no, no--everything seems to be okay."
"Guess, maybe I haven't been getting enough sleep, Mr. Wayne," you say, and pat your codpiece. Terry is finally getting his well-needed rest. You hope you can get the hang of his body before he wakes up, and tries to take it back.