Sometimes I get the feeling that all the writers for primetime television hang out at the same cafeteria and share jokes and story ideas. I first got this notion some years back, when every sitcom seemed to be making the same “Iron John” jokes about men going off together and beating drums in the woods. Remember when every sitcom included some riff on “Antiques Roadshow”? I shudder at the thought of the “Queer Eye for the Straight Guy” jokes that await us. And last season, both “24” and “The West Wing” invoked the 25th Amendment during sweeps. What gives?

Now we have the peculiar coincidence of both “ER” (9 p.m., NBC) and “Will & Grace” (8 p.m., NBC) offering stories about the medical charity group Doctors Without Borders. Granted, they approach the subject from very different directions — it’s treated as a punch line on “Will & Grace” and with deadly seriousness and reverence on “ER” — but both shows use the organization to explain the absence, or scheduled absence, of major characters.

Tonight’s other highlights

• Eviction No. 3 on “Survivor: Pearl Islands” (7 p.m., CBS).
• Major League Baseball divisional playoffs (7 p.m., Fox).
• Elliot considers her run of bad luck on the third-season premiere of “Scrubs” (7:30 p.m., NBC).
• Grissom scrambles for a new strategy after two murder suspects are found slain on the conclusion of a two-part “CSI” (8 p.m., CBS).
• Contemporary hip-hop artists perform with Chicago blues talent on “The Blues” (8 p.m., PBS).
• A priest with a delicate condition disappears on “Without a Trace” (9 p.m., CBS).
• Scheduled on “Primetime” (9 p.m., ABC): interviews with murder suspect Daniel Pelosi and talk show host Wayne Brady.

Series notes

Shocked about Joey and Rachel, Ross drowns his sorrows on “Friends” (7 p.m., NBC) … Unusual talents emerge on “Steve Harvey’s Big Time” (7 p.m., WB).

A woman who hid behind disguises goes under the knife on “Extreme Makeover” (8 p.m., ABC) … Justin Guarini guest stars on “Run of the House” (8:30 p.m., WB).

Late night

Lisa Kudrow and R.E.M. appear on “Late Show with David Letterman” (10:35 p.m., CBS) … Jay Leno welcomes Lucy Liu on “The Tonight Show” (10:35 p.m., NBC).

Jack Black chats on “Late Night with Conan O’Brien” (11:35 p.m., NBC) … Val Kilmer appears on “The Late, Late Show with Craig Kilborn” (11:37 p.m., CBS).