Very special episode alert! As we’ve been told, tonight marks the last time “The Office” (8 p.m., NBC) will feature Steve Carell as Michael Scott, the show’s star and Dunder Mifflin’s socially inept boss. Fans of “The Office” know that the documentary-style series is a well-oiled improvisational machine. But it remains to be seen whether things will remain funny without the awkward boss to make things painful or whether it will simply be painful to watch “The Office” without him.

TV history is replete with the departure of cast members in supporting roles. The substitution of Dick Sargent for Dick York on the old “Bewitched” sitcom was so legendary that “Roseanne” spoofed it when the show swapped Sarah Chalke for Alicia Goranson in the role of daughter Becky.

But dropping the star and lead character from a series is a little trickier. Nobody ever proposed “I Love Lucy Without Lucy!” Nor did CBS air “Everybody Still Loves Raymond Even After He Left.”

The effort to keep shows on life support after the departure of stars has been spotty at best. Few people remember the last season of “That ’70s Show” after Topher Grace departed. “Scrubs” also limped along without Zach Braff for another year. By the time those shows fizzled out, they already seemed to have been over for years.

One of the oldest axioms of show business is to leave when audiences are still asking for more. The way a series ends says a lot about it will be remembered. Last May, “Lost” ended with legions of fans mourning its loss. In contrast, “24” concluded with a collective shrug with many wondering, “Is that still on?”

On the other hand, last week’s “Office” episode about the Dundie Awards was strong and showed off every character’s peculiar strengths. And if we’re looking for an example of a series that has not only survived but also thrived after the departure of its “star,” we need look no further than tonight’s listings.

Many thought Simon Cowell’s departure would spell doom for “American Idol” (7 p.m., Fox). But it remains a ratings powerhouse.

It’s not that many of us don’t miss the persnickety Brit. This season’s cheerleading panelists seem to have forgotten that the word “judge” is a verb as well as a noun.

Tonight’s other highlights

• “Wipeout” gives way to a special episode of “20/20” (7 p.m., ABC): “The Royal Wedding: A Modern Fairy Tale.”

• The “Dick & Jane” killer resurfaces on “CSI” (8 p.m., CBS).

• An advertising executive learns to stop lying and pays for the decision with his life on “Bones” (8 p.m., Fox).

• Jerry’s artwork raises eyebrows on “Parks and Recreation” (8:50 p.m., NBC).

• Two bungled burglaries establish a pattern on “The Mentalist” (9 p.m., CBS).

• Liz sees redecorating as a path to fulfillment on “30 Rock” (9:30 p.m., NBC).

• Rapper Cory Gunz gets his own documentary series “Son of a Gun” (10 p.m., MTV).