We've used enough questionable substances to make the specific timeline of the last 20 years a bit sketchy. But we're pretty sure Big came out before the Segway.
Regardless, this Zoltar costume/car employs a Segway to mysteriously float through the streets, making the old young and the young old with no discrimination whatsoever, all while Zoltar's voice is modulated for the full Zoltar effect (though wasn't he a quasi-mute who printed answers on cards in the movie?).
Protip: only wish to be younger. Because if you're suffering arthritis only to find Zoltar broken down, well, Blue Cross won't exactly cry you a river.