I was going to say something like: "If you want to see both Shirley Jones and Shirley Knight in the same movie, then shirley this would be your only choice." Then you would say "Don't call me Shirley." And we'd both have a good hearty laugh.
But it turns out that the Shirleys also appeared together in 1979's universally-panned Beyond the Poseidon Adventure. Gosh, I love the IMDB, even when it spoils lame jokes.
Anyway: Grandma's Boy. It's not good clean fun. It's filthy. To quote the MPAA: "drug use and language throughout, strong crude and sexual humor, and nudity." And that's for the rated version; the DVD adds in extra filth. It's not a great movie for kids looking for role models. Or even young people. If I were on the movie rating board, I'd probably give it an NC-40 rating.
But it's a really pretty good crude comedy, revolving around Alex, a 35-year-old video game tester, whose life revolves primarily around games, marijuana, and self-abuse. Largely through the poor financial choices of his roommate, Alex finds himself in need of lodging; his only choice is to move in with his grandmother (played by Doris Roberts) and her housemates (the Shirleys). Add in a set of wacky co-workers, and the movie practically proceeds on autopilot toward its conclusion.
You also might want to read Reihan Salam's funny and perceptive review, originally published in Slate. I've learned that Reihan and I seem to be on the same wavelength; he deems Grandma's Boy "the most thoughtful meditation on the plight of the beta male that I've ever seen." Okay. That makes me feel better for liking it.