He's actually much more useful as a car than a robot.

One hesitates to mention right off the bat that “Bumblebee” is a “Transformers” prequel, lest discerning readers assume “Bumblebee” is bad and should be ignored. But it is a prequel, and if the other “Transformers” movies had been like this — smallish in scale, focused on a few characters, under two hours, under 300 decibels, and made by a filmmaker instead of a sentient carnival Tilt-a-Whirl — they, too, might have been enjoyable fantasy adventures.

Set in 1987 and backed by era-appropriate pop hits, “Bumblebee” follows the “E.T.” and “Iron Giant” template, albeit with less sentimentality. When the alien planet Cybertron is overrun by the Decepticons (robots that transform into cars and/or planes and are evil), the leader of the Autobots (robots that transform into cars and are good) goes into hiding and sends a soldier named B-127 to Earth to lay low and await further instructions. But B-127 loses his memory and his voice in an altercation with a Decepticon before turning into a yellow VW Beetle and ending up at a junkyard.

It is there that he’s found by 18-year-old Charlie (Hailee Steinfeld), a car buff who is a girl but named Charlie so you’ll know she’s kind of a tomboy. She lives with her mom (Pamela Adlon), doofus stepdad (Stephen Schneider), and annoying little brother (Jason Drucker) and has been wanting a car to replace the moped she uses to get to her job at the Hot Dog on a Stick booth at the local amusement park. She misses her dad, who died not long ago, and has thrown away her diving trophies because she associates the sport with him. In other words, she could use a friend and a new form of transportation.

Charlie and B-127 are initially afraid of each other — and if you think you won’t feel sympathy for a 12-foot robot with highly expressive mechanical eyes cowering in the corner of a garage, think again. They warm up to each other, she names him Bumblebee, and he starts trying to talk by tuning his radio dial to songs with lyrics that fit the situation. She tells him to always be a VW Beetle when others are around, and to only be a robot when they’re alone. “Oh, you want me to hide part of who I am so that YOU won’t be embarrassed??” Bumblebee says in an alternate version of this movie where being a Transformer is a metaphor for homosexuality.

Meanwhile, the U.S. Army, in the person of John Cena, is on the lookout for the space-robot that fell to Earth in the middle of a training exercise a while back. John Cena and the military are thus receptive when two Decepticons, Shatter (voice of Angela Bassett) and Dropkick (Justin Theroux), arrive and tell them B-127 is a dangerous fugitive and they should help them find him. This is a lie, of course, and John Cena is skeptical — he points out, as no one ever has in this franchise, that they’re called DECEPTICONS, for crying out loud — but anyway, the search is on.

Also in the mix is Memo (Jordge Lendeborg Jr.), a nice boy Charlie’s age who lives across the street from her and works at the churro booth across from Hot Dog on a Stick, who stumbles onto her and Bumblebee’s secret while nervously asking Charlie on a date. Now she has a partner for the second half of the movie, when the two of them and Bumblebee fight the Decepticons and the Army. They also enlist Bumblebee to help apply toilet paper and eggs to the home and car of a mean girl who made fun of Charlie for having a dead father. Bumblebee really gets into smearing eggs on the car and ends up dancing on top of it, crushing it. Against all odds, this speechless space-robot has an endearing, childlike personality.

“Transformers” impresario Michael Bay produced this friendly prequel, but it was directed by Travis Knight, who made “Kubo and the Two Strings” and worked on Laika’s other stop-motion ‘toons (“Coraline,” etc.), with a screenplay by Christina Hodson (“Unforgettable”). Thanks to seamless special effects, the computer-generated Transformers seems to have weight and mass and occupy real space, making it impossible (for me, anyway) to tell when it’s digital and when actual models or animatronics were used.

More importantly, while the story has no shortage of fun mayhem, there’s no widespread destruction or cacophonous free-for-alls, no sense that the action is the whole point of the movie. The point is the friendship between the alienated young person and the alien, both vulnerable but resilient. I don’t want to oversell it, but for a holiday lark aimed at young people, this is a pleasant, unassuming little surprise.

Crooked Marquee

B (1 hr., 53 min.; PG-13, a little profanity, lots of fantasy action violence.)