To snip or not to snip? That’s the question facing Marieta (Mónica Cervera), a transvestite hooker-with-a-heart-of-gold looking to ditch her “dangler,” in this shabby movie-musical. A would-be diva, Marieta is living platonically with Tomás, a strangely anemic dwarf, when an inconvenient case of narcolepsy that has her waking up on the streets of Madrid leads her to look for safer work. Meanwhile, Marieta’s zaftig neighbor Berta plots their mutual escape to Brazil in a perfunctory subplot that sets up the should-she- stay-or-should-she-go-now denouement. The musical numbers are dreadful and the jokes barely register, but more disappointing is how rote the exploration of the transgender dilemma is. Lacking the campy excellence and unexpected poignancy of Hedwig and the Angry Inch, the movie is one long, formulaic drag. Eventually, Marieta meets a hot grocer with a “peach ass” who likes her package, but though she’s smitten with him, her longing for a pussy prevails. There are a few moments worth perking up for, such as the bizarre techno-goth send-up of the “Thriller” video, but the rest of 20 Centimeters is a flaccid bore.