This is not even close to the funniest thing Gilbert has done on Howard Stern. The best moments were when he portrayed the Pope as Bela Lugosi's Dracula, impersonating and mocking Jerry Seinfeld when he didn't show up for an interview, and doing his impersonation of Andrew Dice Clay, which is one of the best impressions ever.
From what I've read and heard Gottfried was doing his impression of Seinfeld way back before that guy became a household name and was just another comic on the circuit. I also recall a bit he'd done here and there about David Brenner and Seinfeld having a conversation.
"You know what's weird Jerry? You know what's weird? You know what's weird, Jerry? All of these people wearing shoes. You see all of these people wearing shoes? Isn't that weird Jerry? Isn't that weird?"
"Whyyyyyyyyyyyyyy do PEO-ple WEAR shoes? What IS IT with this SHOE THING? IS IT TO PROTECT THEIR FEET? I meeeeean, WHAAAAAT IS TH' DEAL?"