Michael Peña stars as a trigger-happy FBI agent from Miami who, on the trail of a group of bank robbers with a hidden connection to the Los Angeles police, goes undercover as Officer Frank Poncherello at the California Highway Patrol Division (or CHiPs). There, he meets Officer Jon Baker (Dax Shepard), a former motorcycle racing champ who’s only joined the force as part of a flailing attempt to win back the affections of his wife, Karen (Kristen Bell, Shepard’s real-life spouse). Shepard, who made an early mark with the reality series Punk’d before graduating to the movies, exercises an auteur’s control over CHiPs. As well as its co-star, he’s the writer, director, co-producer and, unless our eyes are deceiving us, he’s had a hand in co-ordinating the stunts, too. The latter aspect which proves to be the movie’s strongest suit; the writing, on the other hand – that’s another story. There’s an early exchange between Baker – the honest yet wet-behind-the-ears rookie cop – and a younger female officer, Ava (Rosa Salazar), who’s signposted as his love interest. From memory, it goes something like this: Baker: Hi. Ava: That’s a nice bike. Ava: Yeah, it’s cool. Baker: Good. Ava: Yeah. I like bikes. It’s one of those scenes where you can’t tell whether it’s improvised or scripted; whether the conversation is really going anywhere, or whether the actors don’t realise the camera’s running. CHiPs is full of these moments: loose, rambling dialogue scenes where characters choose a subject, riff on it for three or four minutes, and hope they’ll strike comedy gold. These topics include: how often Baker uses the bathroom, Ponch’s sex addiction, lycra leggings, dating apps, Baker’s crotch, Baker’s conniving wife, one of Ponch’s sex partners, motorcycle engines, and Baker’s crotch again. In its R-rated combo of violence, bromance, improv and celebrity cameos, CHiPs‘ template is plainly 21 Jump Street, which proved to be a big hit for Channing Tatum and Jonah Hill. But where that adaptation of an old TV show was enlivened by plenty of self-awareness and good-natured chemistry between its leads, CHiPs is pretty much levelled by its wildly misjudged tone and sleazy humour. Shepard and Peña aren’t necessarily terrible as the leading couple, and there’s a scene where we learn that Shepard’s character has so many injuries from riding motorcycles that his limbs barely work when it rains. It’s a moment that really humanises the character, and there’s a shiny-eyed earnestness to Baker that makes you think, just for a moment, that CHiPs might find its feet as a scattershot comedy. But then Ponch shows up, the conversation turns to Baker’s crotch again, and that hope is but a memory. Shepard’s fixation on his motor-mouthed duo is such that his supporting actors barely get a look in. Such comedy stalwarts as David Koechner and Maya Rudolph get precisely one, awkwardly unfunny scene each. Kristen Bell has three, and they’re all identical – she shows up, says something nasty and exits stage right. D’Onofrio, who’s far too good for this nonsense, should make for a fine villain, but his big entrance is horribly botched (the dialogue doesn’t even match his jaw movements), and he spends the rest of the film looking a bit lost. After you’ve sat through all 101 minutes of CHiPs‘ laboured comedy and crotch gags, you’ll probably feel the same way. CHiPs is out now in UK cinemas.