Tonight marks the last Thursday of the network TV season, which concludes next Wednesday. Long ago dubbed the night of “Must-See TV” by NBC back when it dominated the night with hit comedies, Thursday nights remain the most popular and competitive evening of the week.

“CSI” and “Grey’s Anatomy” remain two of the most popular shows on television. “Ugly Betty” and “Shark” were among the most successful new launches of the year. Last week, CBS beat ABC in total viewers for the night, but ABC won the most viewers aged 18 to 49, despite a poor showing for the summer series “Traveler” and the airing of the next-to-last episode of the once-powerful but fading “Survivor.”

NBC, the network that all but owned Thursday evenings for four decades, came in fourth in total viewers and third in the 18 to 49 viewers. To put NBC’s plight in gruesome perspective, more viewers watched a 90-minute version of “Are You Smarter Than a 5th Grader?” on Fox than the season finale of “My Name is Earl,” and regular episodes of “The Office” and “Scrubs.”

Despite such a lackluster showing, NBC has committed to its existing Thursday-night schedule for next fall, when it will air “Earl,” “30 Rock,” “The Office,” “Scrubs” and “ER.” Of these renewals, only “Scrubs” is a slight surprise.

I admire NBC for sticking by “Earl,” “Office” and “Rock,” but the network must be banking on the fact that their comedies remain popular among TiVo and DVR operators and among those who download shows via the Internet. Because when “5th Grader” beats you, you’re no longer competitive in a broadcasting sense.

¢ Part of NBC’s broadcasting strategy has been to expand the role of cheaply made game shows in the early hours of prime time. This is hardly new. In fact, CBS salutes a man who knows a thing or two about the genre. “Bob Barker: A Celebration of 50 Years on Television” (7 p.m., CBS) focuses on the three and half decades he has been associated with “The Price is Right.”

Tonight’s season finales

¢ While Michael, Jim and Karen compete for a corporate office job, Dwight takes charge as only he can on “The Office” (7 p.m., NBC).

¢ Feelings between Betty and Henry intensify as Wilhelmina schemes and Daniel spirals downward on “Ugly Betty” (7 p.m., ABC). Kristin Chenoweth and Gina Gershon guest star.

¢ Clark takes on Lionel to avenge his threat to Lana on “Smallville” (7 p.m., CW).

¢ Hot on the trail of the “Miniature Killer,” Sara goes missing on the seventh-season finale of “CSI” (8 p.m., CBS). A repeat (9 p.m.) about a missing basketball star follows.

¢ J.D. and Elliot mull their futures, be they separate or together, on “Scrubs” (8 p.m., NBC).

¢ Cristina and Burke’s big day arrives on “Grey’s Anatomy” (8 p.m., ABC).

¢ After the fight between Jake and Sam, the demon seems to have the upper hand on “Supernatural” (8 p.m., CW).

¢ The new chief (Stanley Tucci) wields a cost-cutting ax on the season finale of “ER” (9 p.m., NBC).