Faces in the Crowd, at Improv-Olympic, and Chartreuse, at ImprovOlympic. Second City and ImprovOlympic have launched a lot of careers, but for every actor catapulted to fame there’s a dozen who just keep bouncing at the edge of the board. Still, many of them choose to remain “underground,” like the producers of zines and indie rock, for the immediacy and authenticity offered by small-scale performance in a street-level community. (Then again, as with zines and indie rock, many simply plateau at the local level.) As a result the late-night B-stage shows at both these improv institutions can range from unassumingly brilliant to boringly proficient.

Faces in the Crowd, directed by the able Peter Gwinn, has a simple but elegant structure: continuous fast-edit improv scenes center around a single player in a single role until another player’s incidental character steals focus and becomes the new center, a process repeated for each of the eight cast members. Naturally enough, the characters that stick are freaks of one variety or another–“the people we remember, but that we never get to know,” according to the program. Fleshing out a role in this collagelike format is much harder than it looks, and while all the performers displayed strong mechanics on the night I attended, several portrayals were sadly flat. But thanks to a compulsively watchable form and the nonchalant skillfulness of the rest of the cast, it was a funny, engaging show nonetheless.

Chartreuse, on the other hand, seems mostly a case of the devil making work for idle improvisers. A loose sketch-and-variety show hosted (and created) by Faces standout Jason Anfinsen, it’s so lightweight that holding it to any high standard would be unfair, although there wasn’t much to recommend it the night I attended. Anfinsen was tamely amusing in an ongoing routine about impending marriage, but the admittedly competent guest-artist bits–some annoying comic songs by the usually excellent Megan Grano, yet another pointless sketch about an instructional-motivational duo, and a band that was really, thoroughly, um, OK–were pretty dull. Another lineup on another night, however, might easily come together.