Okay then. Suppose we have someone playing the part of an adventurer/yogi who has traveled extensively to the Far East and frames his effects as ancient secrets of yogic disciplines, meditation, and martial arts.
Now give him a reason to do a sponge ball routine.
Hmm . . . .
Change the prop, but not the routine: use small pillows made from sari cloth, one of which is embroidered with Ganesha. "In Mumbai I learned this game . . . ." Or pieces torn from a warm naan that is on the table from the start--allowing the magician to eat the pieces one by one . . . "but look, there is still one more under here."
Morgician's point is well-taken: to make this work, I would think you'd have to change the prop. That sure makes it easier. But B&WI's point is also well-taken: you can still fit the routine into a persona for whom it would initially seem implausible. It is tougher, for sure, and a change in the prop makes it easier, but it is not impossible to do.
Props are a visual anchor. You can ask the audience to imagine they are something else--a small angel or a ball of energy--but they will still see a bright red clown nose, which makes it tougher for them to make the imaginative leap. They'll have to focus on that--"Which one was the devil?"--instead of your magic. As a matter of consistency, your props should visually fit your persona: it makes belief easier for your audience.
Goth sponge ball routine? Use dice and complain about bad luck, and only perform on Friday the 13th. (Isn't that a Goth thing to do?
) The dice might make more noise, but practice might alleviate that--or even turn it into part of the act ("Listen, you can hear the die under this cup when I shake it . . . but it's over here.").
Or for the punkier Goth: make small stuffed pillows with band logos on them held down by safety pins. Reveal nine ten-penny nails in the relevant pillow.
For the Victorian Emo Goth: use tarnished silver cups and satin rosettes that are part of your outfit. Don't talk and make lots of expressive gestures.
Perhaps the I'm So Poor It Makes Me Weep Goth: use dried beans and styrofoam cups, then finish off with an unexpected Russian Roulette routine. "This is dumb. *smash* Screw this. *smash* *aim at third cup* *hesitate* *knock over third cup to reveal upended razor blade that wasn't there before* Whoa."
In other words: you're both pretty now stop fighting.