In “Home,” the latest adventure from DreamWorks Animation, the misfit alien protagonist is called Oh (“The Big Bang Theory’s” Jim Parsons) simply because that’s the resigned reaction everyone has when he’s around. “Oh,” his brethren say with deep indifference at his desperate, over-the-top attempts to fit in and make friends. It’s meant to turn into something positive by the end of the film. Unfortunately, “oh” is also the experience of watching “Home,” an earnest exercise that falls flat, despite the best of intentions.

The film, adapted from Adam Rex’s beloved kids book “The True Meaning of Smekday,” tells the story of an isolated alien race — the Boov — who are consistently staging elaborate (albeit friendly) takeovers on planets throughout the galaxy as they run from an intergalactic enemy. Led by the cowardly, arrogant Captain Smek (Steve Martin), the Boov are six-legged creatures with wide-set eyes and pig tail ears who change skin colors with their moods and speak in a bizarre, jumbled, contraction-free version of English.

For the most part, the Boov are an ornery bunch who keep to themselves. Oh is the exception. After the Boov’s invasion of Earth (in which all the humans are forcibly relocated to a new settlement so that the aliens can have their homes), Oh sets the plot in motion by accidentally emailing a party invitation to the entire galaxy (including their enemy).

Suddenly a fugitive from his own people, he eventually teams up with Gratuity “Tip” Tucci, (Rihanna), a 12-year-old girl who avoided the relocation suction tubes and was separated from her mother, Lucy (Jennifer Lopez). Along with Tip’s cat (named Pig), they set off in a flying car powered by slushie machines in search of Lucy.

Director Tim Johnson (“Antz”) has compiled so many appealing elements — including the source material, the voice cast and a bouncy Rihanna-heavy soundtrack — that it’s hard to believe “Home” lands with such a thud.

Most of the problems are with Oh. A combination between Stitch (of “Lilo and Stitch”) and “Star Wars’”Jar Jar Binks, Oh is pretty annoying. He might be earnest and learn a few lessons on his journey, but with his manic, destructive energy and deadly one-liners (“my hands are in the air like I just do not care”), he is also not someone you’d want to keep company with, even for an hour and a half.

While Tip has the makings of a compelling, spirited character, most of that comes through in the animation and the help of well-placed pop songs. Rihanna’s jaded and subdued voice-acting leaves a lot to be desired. In fact, the few successful emotional beats take flight when the film turns into a dialogue-free music video.

As the buffoonish Boov leader, Steve Martin has a few fun riffs, but he seems to stick to the dull script most of the time, imbuing life and enthusiasm into the leaden dialogue where possible. Jennifer Lopez’s role, meanwhile, is almost nonexistent.

Visually, the world of “Home” is somewhat flat and synthetic, even in 3-D. The bright color palette and bubble motifs are appealing, but without the magic of superior animated films, the candy colors start to have a numbing effect by the end.

“Home” has a good heart, and yet, much like Oh, its valiant efforts to be fun just fizzle.