The Groundlings' "When Groundlings Attack" is a sketch comedy and improv bill that won't launch a major assault on your funny bone, but it will give you a mild case of the giggles.
The program tends toward the predictable, but the cast charges undaunted into creative characterizations. There's no real bomb, but there are no fireworks either.
Skits like "Ski Legs" depend on the nervous titters of the audience as two men (Michael LoPrete and Nat Faxon) crawl about the stage because their bodies are too sore from a long day of skiing. "Fascination With Cole," in which two dorky boys (Jim Rash, Faxon) fawn on the cool, leather jacket-wearing Cole (LoPrete), is more silly than clever.
Better is "Marci Makes Things" with Amy Von Freymann as a public-access television host who teaches people how to make things from potato chip bags and old cigarette boxes. It's funny but definitely a cheap shot.