Must See TV: 2010's May Sweep Round-up

This month, Matt Damon pops up on 30 Rock, Fox anoints an Idol and Private Practice promises at least one significant death. Welcome to the May Sweep.

The average viewer doesn't care that May marks a quarterly period when local ad rates are set. The bottom line is, May is one of those periods when the broadcast networks toss a lot of stars, specials and sexy storylines in to grab viewers (read: ad dollars). And being the final month of the 2009-2010 TV season, May means plenty of series and season finales.

Here's a list of what you won't want to miss on your favorite shows this month:

Notable Guest Stars

Olivia-Newton John gets physical with Sue on Glee at 9 p.m. May 4 on Fox. Molly Shannon also guest stars.

Oscar multi-nominee Marsha Mason (The Goodbye Girl) guest stars as Frankie's (Patricia Heaton) mom on The Middle at 8:30 p.m. May 5 on ABC.

Sharon Stone appears May 5, 12 and 19 as Detective Stabler's old partner ADA Jo Marlowe on Law & Order: SVU at 10 p.m. Wednesday on NBC.

Buzz Aldrin, Anita Gillette, Jan Hooks, Patti LuPone and Elaine Stritch guest star on 30 Rock at 9:30 p.m. May 6 on NBC.

Martha Plimpton guest stars as Sheriff Mathis, who teams up with Peter on Fringe at 9 p.m. May 6 on Fox.

Gwyneth Paltrow and Jerry Seinfeld judge others on The Marriage Ref at 10 p.m. May 6 on NBC.

Michael McKean stars as Clark's mom's new boyfriend Perry White on Smallville at 8 p.m. on May 7 on the CW.

Betty White hosts Saturday Night Live at 11:30 p.m. May 8 on NBC and makes yet another comeback as a crotchety librarian on the season finale of The Middle at 8:30 p.m. May 19 on ABC.

Christopher Lloyd guest stars a CIA psychiatrist on Chuck at 8 p.m. May 10 on NBC.

Singers Sheryl Crow, Miranda Lambert and Sarah McLachlan pop up on Extreme Makeover: Home Edition at 8 p.m. May 9 on ABC.

Rob Lowe and Adam Scott play two visiting state auditors on Parks and Recreation at 8:30 p.m. May 13 and 20 on NBC.

Leonard Nimoy guests as Walter's nemesis on part one of the two-part finale of Fringe at 9 p.m. on May 13 on Fox. The two finally meet face-to-face on the other side, with Olivia coming along for the wild ride.

Demi Lovato plays a troubled teen patient and Marion Ross (Happy Days) plays an elderly patient on Grey's Anatomy at 9 p.m. May 13 on ABC.

Mad Men's Jon Hamm is back on 30 Rock at 9:30 p.m. May 13 as Liz searches for a wedding date.

Neil Patrick Harris and Idina Menzel guest star on Glee at 9 p.m. May 19 in an episode directed by Joss Whedon (Buffy, the Vampire Slayer, Dollhouse).

Los Angeles Lakers Kobe Bryant appears on the season finale of Modern Family at 9 p.m. May 19 on ABC.

Matt Damon guest stars as the man of Liz's dreams in the season finale of 30 Rock at 9:30 p.m. May 20 on NBC. Will Forte also guest stars.

Ryan Seacrest, Simon Cowell, Ellen DeGeneres, Kara DioGuardi and Randy Jackson guest-voice as themselves in the season finale of The Simpsons at 8 p.m. May 23 on Fox.

Kevin Jonas plays for charity on Minute to Win It at 8 p.m. May 23 on NBC.

Mayim Bialik (Blossom) guest stars as Sheldon's perfect match on the season finale of The Big Bang Theory at 9:30 p.m. May 24 on CBS.

Olympic Gold Medalist Lindsey Vonn will be on the season finale of Law & Order at 10 p.m. May 24 on NBC.

Season Finales

America's Funniest Home Videos at 7 p.m. May 9 and 16: Two-part finale that offers up the best videos of the last two decades of the show.

The Amazing Race at 8 p.m. May 9 on CBS. Will the cowboys, the brothers or the vapid beauty queen and her model boyfriend be the first to cross the finish line?

Private Practice 10:01 p.m. May 13: May and her unborn baby fight for their lives during surgery and the staff is rocked by an unexpected death.

Survivor: Heroes vs. Villains at 8 p.m. May 16 on CBS. The two-hour finale starts with five remaining castaways and is followed by a one-hour reunion show hosted by Jeff Probst.

Desperate Housewives 9 p.m. May 16: Finale has a couple of housewives in jeopardy, including Lynette at the mercy of killer Eddie and Gaby trying to save Angie from her vengeful ex-boyfriend.

The Celebrity Apprentice 9 p.m. May 16 and 23 on NBC: In an otherwise lackluster season, the drama coming in the finale is whether Bret Michaels, who is recovering from a brain hemorrhage, will show up for the live finale.

Castle at 10 p.m. May 17 on ABC: Castle and Beckett confront their mutual attraction, while mystery writers Stephen J. Cannell, Michael Connelly and James Patterson appear as themselves.

Fringe 9 p.m. May 20 on Fox: Sacrifices are made and both universes may never be the same again after Walter and Olivia visit the other side.

Grey's Anatomy 9 p.m. May 20 on ABC: Promises an explosive two-hour season ender with "a crisis like no other in its history." Mandy Moore guest stars.

Dancing with the Stars 8 p.m. May 25 on ABC: Who waltzes off with the top prize? Tune in and find out.

American Idol 8 p.m. May 25 and 26 on Fox: The first night, the remaining two finalists battle it out in a live performance. The results are revealed on May 26, but not before the Top 12 reunite on stage and a two-hour musical celebration.

Series Finales

Lost at 7 p.m. May 23 on ABC. Take a refresher course with "Lost Recap Special" followed by the big two-hour series ender. End of an era.

24 at 8 p.m. May 24 on Fox: The TV series stops ticking after the two-hour season finale of Day Eight as Jack once again takes matters into his own hands for one last unforgettable job.

Two and a Half Men at 9 p.m. May 24 on CBS. Rumor has it Charlie Sheen won't be back. If things don't change, this might be the last time we see the Harpers.