“That's My Boy” easily achieves a rare feat as the grossest of Adam Sandler's late-model Happy Madison junk, and it gets points for going “all-in”: there are no half-measures in Sandler's race to the nasty, sticky bottom. But all the bodily functions, dreadfully unsexy sex and plopped-in-the-middle sentiment in this father-and-son comedy come off as random, barely considered ideas hurried to the page and screen. This is Sandler doing the bare minimum for maximum profit — again — and throwing movie legends, notable nonactors and noxious pseudo-celebrities into the same mess, seemingly just to prove he can do it.
Sandler and writer David Caspe (“Happy Endings”) bookend “That's My Boy” with toxically unfunny situations, beginning in 1984 with seventh-grade Bostonian Donny Berger (Justin Weaver) being seduced by his teacher, Mary McGarricle (Eva Amurri Martino) — that's “seduced” if you're being charitable, “sexually molested” if you're being legally accurate.
Sure, “That's My Boy” defenders can rationalize this as the logical next step in the Van Halen “Hot for Teacher” fantasy, but it is one thing to be hot for teacher, another thing for teacher to be hot for student.
At any rate, Donny and Miss McGarricle get busted in an act of epically stupid sex, and the teacher, now hilariously pregnant with a 13-year-old boy's child, gets sent to prison. Donny enjoys tabloid fame and is ordered to raise the baby, named Han Solo Berger, maintaining custody until his 18th birthday.
Flash forward 28 years, and Donny (Sandler using an in-and-out South Boston accent) is a has-been strip-club patron with a big tax debt. In order to get out of serving time, he hatches a scheme to harvest some reality television cash by reuniting with Han Solo and Miss McGarricle during a prison visit. So he weasels his way back into his son's life just in time to see Han Solo, an investment banker living under an assumed name and played by former “Saturday Night Live” standout Andy Samberg, get married to a comely shrew (Leighton Meester) at the estate of his boss, played by Tony Orlando (of course).