Timing is everything. What does it mean when NBC returns to its “must-see” comedy block one night after sweeps ends? In contrast, CBS commemorates the evening with a solid block of repeats.

“Scrubs” (8 p.m., NBC) enters its sixth season with an episode that appears to have been written with sweeps gimmicks in mind. Both JD (Zach Braff) and Dr. Cox (John C. McGinley) project their personal problems on patients beset with grave illnesses. This self-absorption is exemplified by the fact that Braff and McGinley don prosthetics and make-up to play their own patients. The sight of the handsome Braff as a homely breast-cancer sufferer is more disturbing than amusing.

¢ “The Office” (7:30 p.m., NBC) falls a bit flat with an episode written by series creators Ricky Gervais and Stephen Merchant. Michael goes overboard when he overhears employees making unpleasant comparisons between work and prison. His efforts at a “Scared Straight” intervention seem absurd even by his cracked standards.

The addition of the sycophant Andy (Ed Helms) to the staff has now burdened the comedy with three clueless buffoons (Andy, Dwight and Michael), who tend to steal time from the show’s best story, the awkward love triangle between Jim, Pam and newcomer Karen (guest star Rashida Jones).

¢ Who says ratings rivalries don’t get personal? On tonight’s episode of “My Name is Earl” (7 p.m., NBC), the hapless Randy decides to take a life-altering step. After his amorous success with the eccentric cat lady (Amy Sedaris), Randy has finally decided to declare his love for Catalina. As a token of affection, Randy plans to make a pinata of movie star Salma Hayek because Catalina can’t stand her. In real life, Hayek happens to be the producer of, and a frequent guest star on, “Ugly Betty,” which airs opposite “Earl” on ABC.

Tonight’s other highlights

¢ Betty and Daniel wrestle with relationships on “Ugly Betty” (7 p.m., ABC). Salma Hayek guest stars.

¢ Jack Nicholson and Adam Sandler team up in the 2003 comedy “Anger Management” (7 p.m., FX).

¢ Meredith’s half sister needs care on “Grey’s Anatomy” (8 p.m., ABC).

¢ Curtis (Forest Whitaker) appears to be stalking Kovak on “ER” (9 p.m., NBC).

¢ Marin returns to Gotham with Alaska on her mind on “Men in Trees” (9 p.m., ABC).