A Million Ways to Die in the West Seth MacFarlane, Charlize Theron, Amanda Seyfried, Liam Neeson. Directed by Seth MacFarlane. Rated R. Opens Friday.

When animated-TV superproducer Seth MacFarlane (Family Guy, American Dad, The Cleveland Show) broke into movies with his 2012 directorial debut Ted, he basically made a raunchier, live-action version of one of his TV shows, right down to providing the voice of an animated anthropomorphic animal (the title character, a talking teddy bear). With A Million Ways to Die in the West, MacFarlane has upped his cinematic ambitions, but he’s failed to improve his joke-crafting, his narrative sense or his acting. In his first major live-action role, MacFarlane stars as Albert, a meek sheep farmer in 1882 Arizona, and one of MacFarlane the filmmaker’s worst decisions is casting MacFarlane the actor in the leading role.

As the voice of a ridiculous cartoon character, MacFarlane can be effective, but even though Million Ways is often cartoonish, the heart of the story is a familiar love story, and MacFarlane can’t pull off the role of a romantic leading man. After getting dumped by his girlfriend Louise (Amanda Seyfried), Albert meets local newcomer Anna (Charlize Theron), a tough-as-nails frontier woman who promises to help him stand up to his romantic rival (Neil Patrick Harris) and win Louise back. Of course, Albert and Anna end up falling for each other, which doesn’t sit too well with notorious outlaw Clinch Leatherwood (Liam Neeson), who happens to be Anna’s husband.

That’s a good deal of plot for a movie that’s mostly about poop jokes, and MacFarlane and his co-writers Alec Sulkin and Wellesley Wild (who also co-wrote Ted) have trouble doing the heavy lifting that the story requires. At nearly two hours, Million Ways is way too long for a dumb comedy, and the last half-hour is full of unnecessary detours. Theron is charming, but the rest of the supporting players are either trying too hard or not trying at all, and MacFarlane still manages to fill the movie with celebrity cameos and lazy pop-culture references even though it’s set almost 150 years in the past. As a delivery system for MacFarlane’s brand of lowbrow humor, Million Ways does its job, but as a movie, it’s a complete mess.