Grammer and the Only Fools and Horses star first met when they appeared on stage together in Man Of La Mancha at the London Coliseum in 2019.
“I fell in love,” Grammer told BBC Radio Bristol. “I adore him and he’s one of the funniest people I’ve ever worked with, and I accuse him of being a bit of a sandbagger because you don’t see him coming and all of a sudden he’s getting all the laughs.”
Speaking of the British star’s new character who has been billed as as “an old friend” of Frasier’s, Grammer said: “It suddenly occurred to me when we were putting the show together, we’ve never really seen Frasier in a relationship where he has a great friend.
“He had Niles, of course, but he was his brother and there was a competition underscoring everything they did, and a family connection that got them through some difficulties.
“But this real friendship thing is something we’ve not seen Frasier in... So we’re discovering a man who is still discovering himself, and that is what I find interesting to play.”
This will mark Lyndhurst’s first screen role since his son Archie died at the age of 19 in 2020.
Frasier was originally a spin-off TV show Cheers and remains one of the US’s most successful TV sitcoms. It ran for 11 seasons - between 1993 and 2004 - and won 37 Emmy Awards, including five for best comedy series.
The reboot, which will be available to stream on Paramount+, was first announced in June 2021.
Grammer teased that rehearsals will start in “a couple of weeks” and could begin streaming as soon as July.
The former Star Trek actor also revealed he is working on a new TV show potentially for Channel 4 in which he will “check out restaurants and gastronomy around the provinces of England, rather than London”.