Animal House star Tim Matheson, 76, says he once slept with three women in a day - including Kirstie Alley

Tim Matheson isn't holding back with his new tell-all memoir.

The 76-year-old Animal House star shared in one particularly raunchy passage of his book, Damn Glad To Meet You, that he had once had pre-birthday festivities that included sleeping with three different women in a single day — including a pre-fame Kirstie Alley.

Matheson admitted that the triple trysts happened while he was in Los Angeles and his then-girlfriend was across the country in New York for work.

The day got off to a surprising start, when Matheson writes that a friend of his arrived at his front door in a 'sherry lace top and crotchless velvet panties,' via Page Six.

Although his 33rd birthday was still a day away, he writes that his friend wanted to give him 'an early present.' 

Matheson spares a thought for his long-distance girlfriend, writing in his memoir that he 'really did love this other girl three-thousand-plus miles away...'

However, he adds that the sentiment 'doesn’t mean I wasn’t a pig and an idiot.'

His birthday eve took another surprising turn when another woman showed up on his doorstep.

This time, it was a 'beautiful waitress' he was acquainted with who worked near where he was staying.

After her experiential birthday gift, the Very Brady Sequel star was cooling down when he got a phone call from his friend Kirstie Alley.

'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,' he writes of the film and television star. 'She was also a few years from Scientology and, so, still in her fun Wichita-gal-now-in-LA partying phase.'

According to Matheson, the future star asked if she could drop by his place.

One thing led to another, and then 'Kirstie Alley is naked and we’re enjoying some postcoital conversation in my bed.'

But her visit to his bed nearly coincided with disaster for the former child star, as he heard someone arriving while they were still in bed.

It turned out to be his girlfriend, who had sweetly flown out to Los Angeles to celebrate his birthday.

He writes that he managed to get his girlfriend away from the bedroom and kept her occupied just long enough for Alley to 'magically' disappear.

The Cheers star would go on to become a massively popular actress for years. She died in 2022 at age 71. 

Although his birthday celebrations appear to be among the most salacious revelations from his well-reviewed memoir, Matheson also reportedly details dating the iconic English model-turned-actress Twiggy.

He also writes of a period in which he dated a 'gorgeous woman named Georganne' who was living with her sister at the time.

During one visit to see her, Tim and Georganne saw her 'bib sis' reading on her bed, at which point he reveals she was far from an anonymous sister.

'Her sister was Cher. The Cher,' he writes, explaining that 'Georganne had not bothered to reveal the identity of her sister to me … It [was] startling to say the least.

Matheson, who was a loose inspiration for Skyler Gisondo's suave aging child actor in Licorice Pizza, has been married three times. 

He was first married to the Canadian actress Jennifer Leak from 1968 to 1971, then he married again to Megan Murphy Matheson from 1985 until their 2010 divorce. 

Most recently, he tied the knot with Elizabeth Marighetto in 2018.

His career began in his early teens with roles on television, and he also voiced the title character in the animated adventure series Jonny Quest. 

Later, he appeared with Lucille Ball and Henry Fonda in Yours, Mine and Ours (1968), opposite Clint Eastwood in Magnum Force, and in the iconic comedy Animal House.

Steven Spielberg later hired him for his misbegotten comedy 1941, and he had major roles in comedies including Fleetch, Black Sheep and A Very Brady Sequel. 

More recently, he appeared in Jumanji: Welcome To The Jungle and the remake of Child's Play.