“Animal House” star Tim Matheson revealed he once slept with four women in the same day, including Kirstie Alley.

Matheson made the raunchy revelation in his memoir, “Damn Glad to Meet You.” At the time, the actor was dating an Emmy-award winning actress who remained unnamed in the story.

Matheson began the tale on the day before his 33rd birthday, when he was visited by a woman he’d “spent time” with before.

“‘Hey, hey …'” Matheson recalled her saying in the memoir. “‘So … I know it’s your birthday tomorrow. And … I wanted to give you an early present.’ Opening the door fully, I’d decided it would be rude to send her away; we soon got amorous on the downstairs couch.”

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Tim Matheson revealed in his memoir that he once had sex with four women within 24 hours.  (Ralph Dominguez/MediaPunch via Getty Images)

A couple of hours later, Matheson was visited by another woman while his unassuming girlfriend was in New York City.

“Now it’s 2:30 in the afternoon, my Adam & Eve paramour was long gone, and there’s another quiet knock at my door,” he wrote. “At my doorstep this time, a beautiful waitress I knew who worked a couple of blocks down the street. ‘I have to work all tomorrow,’ she said, pouting her puffy waitress lips. ‘So I wanted to wish you a happy birthday today.’ ‘How sweet,’ I said. ‘What’d you have in mind?’ She stepped inside and reached for my belt.

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Tim Matheson recalled his girlfriend walking in after he and Kirstie Alley had sex. (Getty Images)

“Hours later, I’m settling in for the evening of some well-deserved rest with a glass of wine and listening to Eric Clapton’s latest album, when the phone rings. ‘Tim!’ ‘Who is this?’ ‘You know damn well who it is,’ the voice on the other end replied. And I did. No one else in Hollywood had Kirstie Alley’s voice. Kirstie hadn’t hit yet and was still two years from ‘Star Trek II: The Wrath of Khan’ and five years from ‘Cheers’ and a superstar career. She was also a few years from Scientology and, so, still in her fun Wichita-gal-now-in-L.A. partying phase. It was a good phase for her.”

After inviting Alley over, the pair hooked up and were chatting when interrupted.

“My New York girlfriend now stood in the threshold of the bedroom,” he wrote in the memoir. “New York was still probably twenty-eight hundred miles away, but she unquestionably was not.”

Tim Matheson turned 33 in 1980. (Ron Galella, Ltd./Ron Galella Collection via Getty Images)

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Now Matheson had Alley, who died in 2022, in his bed and his girlfriend standing in his doorway. The New York City actress fled the house, and the actor caught up with her in the driveway.

“I flew out to surprise you on your birthday,” Matheson recalled her saying. “I wanted to be here at midnight to be the first person to wish you happy birthday.”

After groveling for an hour, Matheson somehow coaxed the girlfriend into his bed.

Tim Matheson is known for “Animal House,” “Burn Notice,” “The West Wing” and “Virgin River.” (Glenn Watson/NBCU Photo Bank/NBCUniversal via Getty Images via Getty Images)

“I led my girlfriend to the bedroom and began to tell her, honestly, how much I loved her. I tried calming her and caressing her – actions which weren’t rebuffed and that started to lead to some promising makeup sex,” he wrote.

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“The kind that might even open a newer and deeper level of our relationship. The realization that she was so much more important to me than I’d ever imagined drove me to open up more and increased my sexual ardor. She started to take her clothes off, and I’m thinking, I’ve really messed this up and I need to make genuine love to this woman. That I’d been practicing all day didn’t guarantee much. It sufficed.”