Second bananas should not become first bananas — even if they enjoy eating bananas and saying “Banana!” and kind of look like bananas. That is the lesson of Minions, which takes the lovably inept sidekicks from the Despicable Me series and thrusts them into the spotlight to punishing effect. In the right context, the Minions can be amusing. But the right context is definitely not this rambling 90-minute feature.

The film follows three particular Minions — Kevin (tall), Stuart (one eye), and Bob (short, likes his teddy bear) — and also tells the origins of the Minions as a species. Throughout history, these little sentient Twinkees have wandered the planet looking for a master to serve. After many unsuccessful years, the main Minion herd sends Kevin, Stuart, and Bob as emissaries out into the world of 1968 to resume their search. Why 1968? Mostly because it gives the film an excuse to fill its soundtrack with classic ’60s rock tunes as an olive branch to bored parents.

Eventually the Minions’ travels lead them to the swamps of Orlando. Today, the city is home to the Despicable Me: Minion Mayhem ride at Universal Studios. (What a crazy coincidence!) In 1968, it hosts “VillainCon,” where our mustard-hued heroes find two potential evildoers to work for (and sabotage repeatedly to mild comic effect): Scarlet Overkill (Sandra Bullock), supposedly the world’s greatest super-villain, and her inventor husband Herb (Jon Hamm). In order to earn Scarlet’s trust, though, the Minions must first prove their worth by retrieving the Crown Jewels from the head of Queen Elizabeth (Jennifer Saunders).

Directors Kyle Balda and Pierre Coffin (who also voices the Minions) and writer Brian Lynch want the Overkills to recreate the dynamic from the previous Despicable Mes between the Minions and their lovably evil boss Gru. On that front, they fail spectacularly. Scarlet and Herb are complete whiffs as characters, and Bullock and Hamm’s voice work isn’t much better. Hamm does a passable T.J. Miller impression, but give him credit for at least trying something; saying Sandra Bullock phoned in her entirely forgettable turn as Scarlet would be an enormous insult to phones, a useful communication tool utilized by people all over the world.

Without any worthwhile human characters to shoulder the load, it falls to the Minions to carry Minions. Kevin, Stuart, and Bob are cute and occasionally amusing — the prologue, which charts their quest for an evil master through ancient history, has a couple of decent sight gags — but they’re simply not equipped to carry a full-length movie. They only speak in their own curious language — which sounds like a mixture of Italian, Spanish, French, and a kid making nonsense noises after sucking on a helium balloon — so forget about the possibility for any verbal humor, let alone any character development or growth. They also seem to be immortal, and can’t be hurt or killed, so there’s no tension to anything onscreen either. The Minions have just one joke — they act silly and screw stuff up — and Minions is that joke 6,000 times in a row (plus one fart joke). It’s like trying to milk an entire feature — and trying to draw some kind of satisfying emotional arc — out of a Road Runner short.

A certain Looney Tunes influence does cut through the bland plotting from time to time; the Minions themselves spread anarchic weirdness wherever they go, and their goofy vibe can be pretty infectious. Steve Coogan also makes a fun (albeit too brief) appearance as Professor Flux, a mad scientist who builds a time machine and recruits future versions of himself to help him take over the world. But a lot of Minions falls flatter than Bob as he scurries away from Scarlet Overkill’s lava gun. The voices are unimaginative, the new characters are throwaways, and the story’s a total bust. Basically this is the kids movie version of U.S. Marshals, the spinoff of The Fugitive that took the Tommy Lee Jones comic-relief cop that everyone loved and gave him his own starring vehicle that everyone hated. Just let sidekicks be sidekicks.