The actor’s wife, Natasha Gregson Wagner, has already appeared on the show and on Friday’s season finale airing on UP TV, Watson’s real-life father-in-law, Robert Wagner, makes a guest appearance playing the love interest for Raquel Welch.
Watson tells PEOPLE having his famous father-in-law on set was not only a treat for him but for the entire cast and crew.
“His call time was earlier than mine so when I got on set, every single woman was just gushing over him and telling me how charming he is. How wonderful he is,” says Watson, 43. “Everybody loves RJ!”
On the show, Watson plays a single dad raising three daughters, and he has plenty of real-life parenting experience for the role. The former 7th Heaven star and Natasha, who’s mother is legendary actress Natalie Wood, welcomed their daughter Clover in 2012 and Watson has two other sons — Oliver, 12, and Felix, 9 — from a previous relationship.
Watson recalls when he first began dating Natasha (whose father is Richard Gregson) that she told him she felt he would get along great with her stepfather.
“I remember her saying, ‘You definitely have some similarities to my Daddy Wagner,’ ” says Watson. “I didn’t know quite what that was and I still don’t quite understand, but I just know we get along really well.”
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Wagner echoes the sentiment telling PEOPLE: “I can tell you this, I could not have a better son-in-law!”
Date My Dad wraps its first season Friday at 9 p.m. ET on UP TV.