Exuberantly written and directed by Jordan Roberts, "3, 2, 1 ... Frankie Go Boom" is a vibrantly vulgar comedy that never hangs around to admire its own cleverness. With wham-bam timing and unisex jokes, Roberts races us through a jampacked tale of erectile reluctance, brotherly betrayal, Internet disaster and accidental romance.

Equally indebted to actors and script, the film centers on Frank (Charlie Hunnam), a writer whose incorrigible brother, Bruce (Chris O'Dowd) — an aspiring filmmaker once dedicated to posting humiliating videos of Frank on YouTube — is now clean and sober. Returning to Los Angeles for a fraternal reunion, Frank is assured by Mom (Nora Dunn) that the brother who made his life a misery has changed. Let's see how that goes.

Featuring hilarious against-type turns from Ron Perlman as a magisterial transsexual and Chris Noth as an aging star obsessed with maintaining his camera-ready rear, "Frankie" flirts with farce but never betrays the generosity of its emotions. And though the gifted Lizzy Caplan, as Frank's goofily messed-up squeeze, is mostly sidelined by the brothers' dysfunctional shtick, her contributions are critical to a story that may be bro-centered but definitely isn't bros-only.