Review | How I Met Your Mother

Credit: Sonja Flemming/CBS

Airs Monday 2/7

More Katy Perry! The Grammy hopeful guests on the sitcom as a surprisingly naive bombshell. Exhibit A: She tells Barney (Neil Patrick Harris) and the gang she feels safe in her apartment because the manager put a camera in her shower. (CBS, 8 P.M.)

--JOHN GRIFFITHS