Ugly Betty

(8-9 p.m., 6ABC) - Wilhelmina's (Vanessa Williams) effort to shake her "mean girl" image suffers a setback when she scuffles with an elderly woman over a cab. Not just any elderly woman - beloved octogenarian actress Betty White (guest-starring as herself). The other Betty (America Ferrera) agrees to an unusual double date.

Scrubs

(9:30-10 p.m., NBC10) - The doctors of Sacred Heart become fair game for patients on a Web site where they rate their physicians. Kelso's (Ken Jenkins) motivation for enrolling the hospital is improving patient care, but Turk and Cox (Donald Faison, John C. McGinley) are more interested in the race for No. 1.

Without a Trace

(10-11 p.m., CBS3) - She's done her time, but apparently someone doesn't think she's been punished enough. Jack (Anthony LaPaglia) and his colleagues search for an ex-con who disappeared after returning to the prison to visit a friend.

ER

(10-11 p.m., NBC10) - In the series' 300th episode, the ER staff marks the milestone not with a party but with a religious service. It's Julia's (Reiko Aylesworth) idea; she wants to bless the ER and the patients who died. Peter Fonda guest-stars as an accident victim's husband who meets someone from his past at the hospital. A death sends Kovac and Abby (Goran Visnjic, Maura Tierney) to Croatia.

Barbara Walters Presents the 10 Most Fascinating People of 2007

(10-11 p.m., 6ABC) - Justin Timberlake, Jennifer Hudson and Victoria Beckham are among the famous faces on Walters' short list this year. Others are former President Bill Clinton, actress Katherine Heigl, and MySpace cofounders Tom Anderson and Chris DeWolfe. Who's No. 1? You'll have to tune in to find out.