If you’re one of the few who saw “Gnomeo & Juliet,” you may remember it as a sunny surprise in the midwinter of 2011. Despite its dubious premise — a version of Shakespeare’s famous teen romance, but with garden gnomes — the movie turned out to be a lively little comedy with a strong voice cast (James McAvoy and Emily Blunt played the terracotta-crossed lovers) and a smarter-than-average screenplay. The Elton John soundtrack seemed unnecessary, but hey, he was a producer.

Fans of that modest box-office success may have at least semi-high hopes for the follow-up, “Sherlock Gnomes.” McAvoy and Blunt are back, alongside Johnny Depp voicing a brilliant but arrogant Sherlock. There’s some potential for literary humor among the kid-oriented jokes here, but alas, “Sherlock Gnomes” doesn’t have nearly the wit or charm of the original.

The film’s world has been stretched out of plausible shape. Where the first film simply asked us to believe in garden gnomes that come alive at night, “Sherlock Gnomes” must establish a complicated rivalry between the lawn-ornament Sherlock and the pie-company mascot Moriarty, who for some reason preys on gnomes. (Jamie Demetriou plays Moriarty with generic U.K. cheekiness.) When the citizens of Gnomeo and Juliet’s kingdom go missing, Sherlock and his sidekick Watson are on the case.

An interesting side-note: Chiwetel Ejiofor, a Nigerian-British actor, plays Watson, who in keeping with tradition is an old white fellow. Is that colorblind casting, whitewashing or something else entirely? It might not be a question if the film didn’t also bring in such ancient Chinatown stereotypes as a saltshaker (James Hong) who splutters in pidgin English. Here’s a more appealing twist: Sherlock apparently once dated a doll, Irene (Mary J. Blige), who moonlights as a pop singer in the vein of, well, Mary J. Blige. She sings a new John-Taupin tune, “Stronger Than I Ever Was.”

A few behind-the-scenes factors may be working against “Sherlock Gnomes.” For one, Disney is no longer involved. Director Kelly Asbury, who gave the first film a touch of sweetness, has been replaced by John Stevenson. And new screenwriter Ben Zazove delivers a jumble of ideas, but never warps them into a satisfying story. Rather than humming “Crocodile Rock” as you exit the theater, you’ll be wondering: How did a pie-company logo come to life?