What’s On Tonight: Letterman’s Last Episode And The ‘Supernatural’ Season Finale

The Late Show With David Letterman (CBS, 11:30 p.m.) — After 33 years in late night, David Letterman officially signs off with one final episode. No guests, but tons of surprises. It’s the second time this week we’ll get to mark (weep uncontrollably over?) the end of an era.

Supernatural (The CW, 9:00 p.m.) — In the Season 10 finale, Crowely vs. Rowena reaches the jumpoff and drags Castiel into the fray. Meanwhile, Dean surprises everyone (you, me, everybody…) with a decision regarding the Mark of Cain, effectively altering Sam’s path.

Killer Hornets From Hell (Animal Planet, 8:00 p.m.) — NOPE.

NHL Playoffs (NBCSN, 8:00 p.m.) — Rangers at Lightning in Game 3 of the Eastern Conference Finals.

NBA Playoffs (TNT, 8:30 p.m.) — No Steph Curry tonight, but Cavs at Hawks in Game 1 of the Eastern Conference Finals means LeBron’s on.

Modern Family (ABC, 9:00 p.m.) — The whole clan gets together at Jay and Gloria’s for Alex’s graduation party in the Season 6 finale, but Phil’s in Seattle on business so he’s got to Skype in via robot. Probably should have just hired a surrogate.

Law & Order: SVU (NBC, 9:00 p.m.) — Sgt. Benson’s work-life balance is again at the forefront of the storyline as Baby Noah’s adoption becomes entangled in a case at SVU. Will she be more mom or Sgt. as she and her detectives work to bring down a career criminal? The Season 4 A.S. (After Stabler) finale will tell us.

Big Time in Hollywood, FL (Comedy Central, 10:30 p.m.) — George Costanza helps Cuba Gooding Jr. try to flee the country while Malloy moves closer to the truth, putting Jack and Ben in jeopardy.

LATE NIGHT GUESTS: Patton Oswalt, Bill Kreutzmann and The Tallest Man on Earth on Conan; Halle Berry and Jeffrey Dean Morgan on Corden; David Duchovny, Jeff Foxworthy and Mr. Worldwide, himself, Pitbull on Fallon;  Kimmel goes with a rerun to honor Letterman’s final episode.