Part of the fun of IF is guessing the cameo voice roles

If the voice actors in IF, a whimsical comedy about children’s imaginary friends, had been paid their going rate for appearing on screen, the budget would have broken any bank.

Cailey Fleming (Bea) and Steve Carell (Blue) star in Paramount Pictures' "IF."

If the voice actors in IF, a whimsical comedy about children’s imaginary friends, had been paid their going rate for appearing on screen, the budget would have broken any bank.

George Clooney is in it, as are Brad Pitt, Matt Damon, Emily Blunt, Awkwafina, Phoebe Waller-Bridge, Sam Rockwell, Amy Schumer, Richard Jenkins, Bill Hader and Bradley Cooper.

Part of the fun is finding out who’s who in the cameo voice roles, so I won’t reveal too much. One of the IFs, Keith, is invisible, meaning the on-screen actors trip over his … greatness, perhaps? You can decide who that may be.

Another, Ice, is a glass of iced water, who says he wondered, when a child first imagined him to life, whether he was a metaphor. He soon learned the truth and it is literal and ­ego-popping.

This feel-good movie is written and directed by John Krasinski, who is still best known as Jim Halpert in the American version of the sitcom The Office (2005-13). It’s a change of direction from his previous two: the impressive horror movie A Quiet Place (2018) and its 2020 sequel.

Emily Blunt and John Krasinski attend Paramount's "If" New York premiere. Picture: Getty

His boss in The Office, Steve Carrell, is the main IF. Blue is a purple yeti-like softie.

“He’s the most adorable train wreck,’’ says another of the main IFs, the bumblebee-like Blossom (Waller-Bridge). It’s Blue who identifies the problem that only the on-screen actors can solve. When children grow up they forget their IFs and a forgotten IF, eventually, will die unless he, she or it finds a home in the mind of another child.

Enter 12-year-old Bea (Cailey Fleming). She is in New York because her father (Krasinski) is in hospital for a heart operation. She lost her mother a few years ago and is scared she will have to “say goodbye twice”.

She is rooming with her grandmother (Fiona Shaw), who was once a ballerina. She meets another resident of the apartment block, Cal (Ryan Reynolds), who, though an adult, can see IFs, which is useful as his real-life wife, Blake Lively, is an octopus-like one in this movie.

In short, Bea and Cal set up a matchmaking agency to place abandoned IFs with new children. Most of the IFs live in a retirement home in the Coney Island amusement park. The home is run by a large teddy bear (Oscar winner Louis Gossett Jr, who died in March) .

This plan to save the IFs leads to IF auditions, IF counselling sessions and lots of other amusing silliness. When Bea first enters the retirement home she asks Cal if the IFs are scary. “Worse,’’ he says. “They’re desperate.”

Fleming, a star of the television series The Walking Dead, is capable in the lead role. Reynolds takes his characteristic peaks over the fourth wall between actor and audience. When Bea says he needs help, he replies, “You have no idea how true that statement is, but not in the way you are thinking.”

One of the challenges of making a movie about childhood, imaginary friends, growing up and the loss of innocence is the schmaltz factor. Krasinski does dip into it a few times – when Fiona Shaw returns to her ballet days it far exceeds my low saccharine tolerance – but by and large this is a gentle, heartfelt film for viewers of all ages.

There’s a cartoonish side for the kids and a nostalgia tug for adults. It has a decent twist at the end and the final credits sequence, which includes the invisible Keith, is worth hanging around for.

IF (PG)

105 minutes
In cinemas

★★★