How funny, really, are dick pics? Millions of them must be snapped and shared each year, as inducement or harassment, celebration or shaming. Perhaps Harper's Index could tell us the tonnage of coal mined each year to power the transmission of American crotches. So when a dick pic turns up in a raunchy, R-rated comedy, the shock isn't what we're beholding. The shock is the very idea that we might be shocked, that the penises feel so fussed over and spliced in. Much funnier than the flash of flesh is imagining the studio meetings where studio dopes argue over how many frames we can take. Their prudishness over the surprise dicks meant to jolt some exposition in Spy threw the comedy into brief incoherence; the pics flitted primly past, just a hair slower than subliminal messages. Confused viewers might have thought Tyler Durden had spiked the reel.

Credit hit-and-miss holiday comedy The Night Before, then, for the courage of its dick-pic convictions. The first couple play as the usual wan transgression, like the filmmakers believe there are still Margaret Dumonts around to gasp, “Why, I never!” But for once the movie camera doesn't shy away from what our real-life cameras are down with. Seth Rogen doesn't either — for the second time, he seems to have grown past the comedy of gay panic. The Night Before stars the game-for-anything near-adult Rogen of Neighbors, who was up for jolly stream-crossing watersports with Zac Efron, and not the shrill, sour oaf behind The Interview. His schmo here is flattered and impressed when, tripping on mushrooms, he gets texted a surprise junk shot. After a couple of admiring responses, and a couple more dicks, Rogen (let's not bother pretending his characters' names matter) gets asked if he'd like to handle it. Rather than blanch, he beams, confessing that that's not really his thing but that he did once touch another boy's at camp.

That's all sweet, a sort of one-act illustration of the tension in all Rogen's comedies: If his characters so relish the company of men, why not go whole hog? But it's not exactly funny. In fact, it was only The Night Before's fifth or sixth dick that got me laughing, the one where it's a scene's giddy capper, played like yet another gotcha celebrity cameo.

That run of jokes is The Night Before in essence. (It's directed and co-written by Jonathan Levine, best known for The Wackness and 50/50.) Here's a cohort of likable guys — Anthony Mackie and Joseph Gordon-Levitt — doing the things you expect in Rogen films: hanging, laughing, toking, rapping old songs, learning life lessons already learned in other Rogen films. At first the laughs are Hangover III–spare and the picture is too shambling to lunge for them. But these leftovers warm up eventually. The usual setups at last develop variations, and you might be reminded of why audiences first responded to Rogen back in Knocked Up.

Here, the star peaks in his go-for-broke bad-trip freakouts, first in a bar bathroom, where his character rages against his unborn son, and then in bookending scenes of blasphemy surrounding a midnight Mass. These are funny and courageous and probably caused Sony fits: Last year it was the North Koreans; this year it'll be Fox's not-much-more-reasonable War on Christmas squad. It's not the drugs and the peen and the public puking that's funny — it's what you do with them.

There's a plot, cribbed from Gene Kelly and Stanley Donen's It's Always Fair Weather, that not-quite-a-sequel to On the Town: Old friends reconvene for a ritualistic New York night out, in this case the latest in a series of stoned-dude Christmases, but find that adult life has snuffed their youthful spark. The story's perfunctory, and there's little feeling in it. For long chunks, I forgot that Gordon-Levitt's commitment-phobe songwriter is also the character in the Kelly role, the one we're supposed to be rooting for to find love, here with a grinning dirty-talker played by Lizzy Caplan.

Instead, the film is a revue. There are four musical numbers, one by a pop-star ringer. Michael Shannon turns up as a Christmas Carol–inspired drug dealer, offering the joints of Christmases past, present and future. There are walk-on guest stars, some playing themselves. There's a Santa brawl, a parkour foot chase, some undistinguished vehicular mayhem, creaky speeches about the meaning of friendship and the magic of Christmas, and a Broad City/Die Hard crossover that violates the story's every pretense of believability. (That last one's not a complaint.)

James Franco turns up, at his most ingratiating and self-lampooning, to entice Rogen and Mindy Kaling with the promise of a threesome — and to remind us that, these days, Rogen's feeling open-minded rather than easily skeeved. In fleeting moments, Mackie and Gordon-Levitt exhibit their physical grace, but the dancing and leaping isn't framed to the actors' advantage. (Kelly and Donen weep!) There's so much to pack in that most of these scenes get no time to breathe and build.

The exception: The scenes that come just when most audiences will be aching for the credits to roll. As revues go, this one is indifferently paced, with all the heartfelt and dramatic stuff coming after the big ending. These predictable reconciliations are well acted and, as they go on, studded with unpredictable jokes, recalling the richer emotions of 50/50, which starred Rogen and Gordon-Levitt. But it's all too late, and those moments are followed by yet another song and then a second blowout ending powered by still another celebrity cameo. It's exhausting, possibly a sign of fearful neediness: Boys today show you their dicks first thing and then spend forever trying to prove what nice guys they are.

THE NIGHT BEFORE | Directed by Jonathan Levine | Written by Levine, Kyle Hunter, Ariel Shaffir and Evan Goldberg | Sony Pictures | Citywide

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