Pop quiz: how many American presidents have had to publicly prove they’re U.S. citizens? One, two, or just Barack Obama? Donald Trump has recently attached himself to the “birther” movement questioning President Obama’s citizenship and demanding he publicly show a birth certificate. The nationality witch hunt has sparked responses from President Obama as well as Whoopi Goldberg and Bill Cosby.

Trump — who allegedly plans to run for U.S. President under the GOP ticket — has unfurled a whirlwind of criticisms on President Obama, calling his term “a disaster” and even questioning whether his birth certificate is a valid U.S. document.

In a recent interview with ABC News’s George Stephanopoulos, President Obama directly responded to the billionaire’s comments and would-be campaign saying that he is indeed a U.S. citizen and that “birtherism” will backfire for the Republican Party. “I think that over the last two and a half years, there’s been an effort to go at me in a way that is politically expedient in the short term for Republicans … most people feel pretty confident the president was born where he says he was, in Hawaii,” Obama said. “He doesn’t have horns.”

Additional responses from Bill Cosby and Whoopi Goldberg also blasted the comb-over king.  “I’ve never heard of any white president being asked to show his birth certificate,” Whoopi said during a talk with Trump on The View. “When you become the president of the United States of America, you know that he’s American. I’m sorry. That’s just B.S.”

And as for Bill Cosby? He got straight to the point: Trump is “full of it,” the legendary funnyman told TODAY’s Meredith Vieira. Cosby said he’s tired of Trump’s “will he or wont he” presidential publicity stunts and that he should just “run or shut up.”