Idiotic, infantile and worst of all not very funny, Jared Hess’ “Gentlemen Broncos” is hampered by predictable plotting and equally predictable weirdness.

Hess, who scored with the appealing “Napoleon Dynamite” and then stumbled slightly with Jack Black’s wrestling priest in “Nacho Libre,” has fashioned another Utah tale about another shy teenager, Benjamin (Michael Angarano).

Benjamin is an aspiring science-fiction writer who sublimates his erotic desires in his magnum opus, “Yeast Lords,” a violent tale in which monstrous mammaries shoot enemies.

Hess lets us see this scenario come to life in a low-budget way with Sam Rockwell as the hero.

Benjamin lives in a geodesic dome home with his valiant if kooky single mother (Jennifer Coolidge).

Benjamin submits his “Yeast Lords” manuscript to his idol, bestselling sci-fi author and all-around pretentious idiot Ronald Chevalier (Jemaine Clement of HBO’s “Flight of the Conchords”) at a sci-fi symposium.

Chevalier promptly steals Benjamin’s scenario to resurrect his own failing career.

Unaware of the theft, Benjamin returns home to see his book turned into the cheesiest homemade sci-fi movie made since “Glen or Glenda.” The director (Hector Jimenez of “Nacho Libre”) and his colleague Tabatha (Halley Feiffer, also of “Conchords”) even persuade Benjamin to act in their adaptation.

Seeing it prompts Benjamin to vomit. It’s an extreme reaction but one with which moviegoers might empathize.

New Zealander Clement uses a baleful bleat as he intones every line and stands out in a cast that mostly mugs. The other exception is Angarano’s subtle performance of quiet desperation.

Rated PG-13. At the Kendall Square Cinema.

(“Gentlemen Broncos’ ” gross humor seems ideal for preteens.)