Michael Keaton mourns the loss of “wonderful” Mr. Mom costar Teri Garr

Michael Keaton mourns his death Mr. Mom Co-star Teri Garr, who died on October 29 at the age of 79.

“This is a day I feared and knew would come,” Keaton, 73, wrote on Instagram about Garr, who announced in 2002 that she had been diagnosed with multiple sclerosis.

“Forget how great an actress and comedian she was. She was a wonderful woman. Not only is he great to work with, but he's great to be here too. AND go back and look at her comedic work – man, was she great!!”

The pair played a couple in the classic 1983 comedy about Jack Butler, a married father from Michigan who struggles with domestic responsibilities when he is fired from his job and his wife Caroline (Garr) goes back to work. The film, which marked Keaton's first leading role, also starred the late Martin Mull and Christopher Lloyd.

Talk to PEOPLE during commercials Beetlejuice Beetlejuice Just weeks before Garr died, Keaton fondly recalled the time he worked with her.

“The first thing I'm going to talk about is the fabulous, and I mean fabulous, legend Teri Garr, how amazing she is and how cute she is and how much fun we had in this movie,” he said.

“Regardless of this movie, if you… Just watch it Young FrankensteinMan. And she’s still just amazing,” he added.

Keaton said he knew the script, written by John Hughes, would make a fantastic comedy.

“I remember reading the script. And I remember laughing out loud three or four times,” he said. “And for most people it seems like, 'Well, that's not much.' But ask anyone. Because the other people you're smiling at or you're smiling are reading and kind of thinking about it or imagining it. But when something makes you laugh, it’s encouraging to say the least.”

Keaton was right. Thanks to the chemistry and banter between the two leads, the film received generally positive reviews. The film grossed $63 million at the box office (about $200 million today), making it one of the top 10 hits of the year.

Previously Mr. MomGarr made a name for himself in comedy, starring in hits like “1974.” Young Frankenstein and 1982 Tootsiefor which she received an Oscar nomination for Best Supporting Actress.

Garr died Tuesday “surrounded by his family and friends,” publicist Heidi Schaeffer told PEOPLE.