The embarrassing reason why 'The 40-Year-Old Virgin' was shut down 2 days into production

In an interview featured in his new book, "Sick in The Head," Judd Apatow revealed that his successful directorial debut, "The 40-Year-Old Virgin," initially had some trouble getting off the ground.

Just two days into the film's production, Universal Studios shut the movie down - for reasons that Apatow finds "really silly" in retrospect.

"They thought Steve Carell looked like a serial killer," he said.

"They thought Paul Rudd was fat," added Leslie Mann, Apatow's wife.

In addition, the studio took issue with the fact that Apatow was "lighting [the film] like an indie," and the resulting shut down "cost themselves half a million dollars."

In order to get production going again, the cast and crew had to make some adjustments.

"Paul went on a diet. He literally stopped eating," Mann said. "If you look at Paul Rudd in the speed-dating sequence compared to the rest, he's, like, ten pounds heavier. Then in the rest of the movie his hair looks cute and he's thinner."

As for the titular character, Andy Stitzer, Steve Carell toned down the "serial killer" vibes by making Andy less intense.

"Steve decided the character would be a little more Buster Keaton-esque," Apatow said. "He was low-energy and everyone else was spinning around him."

Eventually, Apatow and the studio patched things up, and the speed-dating sequence stayed in, despite the studio's notes.

"Everything we shot in those first two days became some of the funniest stuff in the movie," Apatow said.

Apatow's book, "Sick in The Head," is available now and features 32 years worth of his interviews with famous comedians - from Jerry Seinfeld in 1983, when Apatow was "just a 15-year-old kid with a tape recorder," to Jimmy Fallon in 2015.