Hard-playing faded ice hockey star Derek Thompson rejoices under the unlikely nickname of the "tooth fairy" thanks to his habit of propelling opponents into the side wall so hard that he knocks their molars out.
But the handle comes back to haunt him when - during a card game with his chums - he runs out of cash and sneakily slips the dollar destined for the milk teeth-shedding daughter of his girlfriend (Judd) from under her pillow and into his pocket. Big mistake.
That night he receives a summons for "Dissemination of Disbelief" - he almost told the youngster that the tooth fairy didn't exist - and is whisked off to Fairyland, a tooth-dispensing HQ ruled over fairly but firmly... by Julie Andrews.
Overseen by his unimpressed case worker Tracy (Ricky Gervais's sidekick Merchant), he's sentenced to two weeks as a tooth fairy, dispensed all over the world armed with a dollar and a special tooth bag.
To make his job easier, he's also equipped with an invisibility spray, shrinking paste and amnesia dust to prevent folk recalling that they've actually spotted the TF.
The plot is as predictable as they come but it's the gentle playing that elevates this from formulaic kids' fare to a genuinely enjoyable family yarn.
Johnson shows he's a natural star with the finely judged sense of comic timing he displayed in The Game Plan working wonders, particularly when playing against human pipe cleaner Merchant's bolshie Brit.
The movie's mantra of "believe-in-your-dreams" could easily have become patronising yet it never does as Derek ruins his relationship with Judd and her kids, learns a few life lessons the hard way and then comes good before the final credits role.
Get your teeth into it.