President Donald Trump was “bewildered” after billionaire Elon Musk awkwardly leaped on stage during his first appearance at a campaign rally alongside the then-GOP candidate in October, author Michael Wolff reportedly revealed in his new book “All or Nothing: How Trump Recaptured America.”

“What the fuck is wrong with this guy?” said Trump following the rally move by Musk, according to an excerpt of Wolff’s book quoted by The Daily Beast.

“And why doesn’t his shirt fit?”

Musk — whose “Occupy Mars” shirt lifted as he raised his hands above his head during his jump for joy — was roasted over the bizarre appearance at a rally marking Trump’s return to Butler, Pennsylvania, the site of an assassination attempt against him just months prior.

Wolff noted that the future head of the nonofficial Department of Government Efficiency had a chance to meet JD Vance at the time but he expressed that he “really” had “no interest in speaking to a vice president,” per The Daily Beast.

Prior to the ask, Wolff reportedly wrote that the billionaire was “wandering about by himself, with only a thin layer of assistants or security” at the rally and his hunger pushed someone to come through with a “bag of pretzel sticks.”

White House communications director Steven Cheung, in a comment to The Daily Beast, referred to Wolff as a “lying sack of shit” who has been “proven to be a fraud.”

“He routinely fabricates stories originating from his sick and warped imagination, only possible because he has a severe and debilitating case of Trump Derangement Syndrome that has rotted his peanut-sized brain,” Cheung said.

Elsewhere in the book, Wolff reportedly revealed that Trump was considering a woman to be his running mate including Fox host Maria Bartiromo as well as Harris Faulkner.

Musk would go on to tell Trump that “his support for the ticket was contingent on Trump’s picking Vance,” the author wrote.

Check out more reporting on Wolff’s new book at The Daily Beast and The Guardian.