Wait, Jimmy Buffett is alive?
With Julia Louis-Dreyfus as his running mate, natch.
She’s the obvious choice. Tons of money, politically involved, already has a huge fan base.
Tom Hanks or George Clooney. Both have the smarts and the political cred - and Clooney, the looks - to be elected to just about anything they chose to run for (although I doubt they ever will).
Trump would run as a Democrat with 100% Democratic positions if he felt he could get the same sort of response from Dem voters that he’s getting from Repubs. Remember the next member of the House Joe the Plumber? He had huge support until he exposed himself as too stupid even for rural Republicans.
Springer must be a lot more famous in Ohio (understandably). He’s seen in the rest of the country as a third rate daytime TV host. Sort of the equivalent of Geraldo Rivera.
Mark Zuckerberg, when he turns 35.
Bill Gates.
Neil DeGrasse Tyson.
Hillary Clinton is the Dems’ celebrity candidate. She and Trump were the only two presidential candidates whose names were widely known to the general public before this election season started. Not even Cruz or Rubio or Sanders had their degree of national name-recognition.
I think the OP meant pop culture celebrity.
I would say Jon Bon Jovi, or Kanye West. Historical side note; in 1999, Warren Beatty flirted with a POTUS run.
That meathead? 
Joe Walsh. He’s run a couple of mock campaigns, for president in 1980 and for vice president in 1992, but in 2012 he said he was seriously considering running for Congress. Maybe now that the Eagles are no more, he’ll make a serious run for political office.
The smoker you drink, the politicker you get. 