The D Train is a comedy that doesn't really work, but at least it doesn't work in interesting ways. It's unpredictable and it takes a lot of risks, some of which pay off.
Jack Black headlines as Dan Landsman, a schlubby and insecure Pittsburgh suburbanite whose remaining self-esteem rests on his position as chairman of the high-school alumni committee. Dan has appointed himself chairman, though, so I'm not sure how official the title really is.
Dan is the sort of grown-up who hasn't gotten over his high-school experience. He was never the popular guy, and it still bothers him. He was, however, kinda-sorta friends with the popular guy—Oliver Lawless, played by the impossibly handsome James Marsden, whose cheekbones are like some Platonic ideal of cheekbones.
Oliver is now a successful actor in Los Angeles, and Dan hatches a plan. If he can fly out to L.A. and convince Oliver to return to Pittsburgh for the upcoming 20-year high-school reunion, he'll be popular by proximity—which is about as much as Dan can hope for these days.
That's the set-up, and what happens from there doesn't play out along the usual trajectory of man-child arrested development comedies. For one thing, Oliver isn't who he seems to be. His career consists of a single (very funny) sunscreen commercial, and otherwise, he's fast on his way to becoming an L.A. showbiz casualty. He takes an alarming amount of drugs and his promiscuity is becoming a real problem. He's not bisexual so much as omnisexual.
The L.A. scenes take a series of hard left turns, including some funny business featuring Jeffrey Tambor as Dan's out-of-touch boss and a quick cameo from Dermot Mulroney, playing himself. The action then moves back to Pittsburgh, where Dan brings Oliver home to his wife (Kathryn Hahn) and teenage son.
It's here that the story begins to collapse under its own weight. Dan's lies pile up to nasty heights, putting his family and his company in real peril. The comedy loses its lightness as we realize that Dan isn't a lovable loser. He's a dangerous loser, reckless and selfish, and Oliver is even worse. The movie wants to go two directions at once—up into high-school reunion clowning and down into Chuck & Buck-style darkness. (That movie's Mike White, not coincidentally, co-produces and has a small supporting role.)
The tone swings around wildly in the second half, finally settling for a hurried, implausible resolution. It's disappointing, because the performers are given individually funny lines and bits, and they know how to deliver them. The movie's title, in fact, references a running gag in which Dan tries to retroactively give himself a cool high-school nickname ("How about D-Money?" "Mmm, sounds forced." "D-Rock?"). The D Train is one of those frustrating A-for-effort movies where you can see what the filmmakers were aiming for—and the distance from that point to where their movie lands.