“CSI: Crime Scene Investigation” (9 p.m., CBS): Get your mask and Spandex ready. For the

“CSI: Crime Scene Investigation” (9 p.m., CBS): Get your mask and Spandex ready. For the milestone 200th episode of “CSI: Crime Scene Investigation,” a fresh murder leads the team into the bizarre world of Mexican wrestling.

“ER” (series finale, 9 p.m., NBC): After 15 seasons of blood, guts and calamity, they’re finally pulling the plug on the series that redefined the medical genre. When it debuted in 1994, “ER” became an instant blockbuster, going on to attract more than 30 million viewers a week during its prime. And while the show’s vital signs have charted downward in recent seasons, it remained capable of delivering compelling medical trauma and romantic drama — along with an occasional surprise (witness the riveting reunion of George Clooney and Julianna Margulies). The two-hour finale airs right after a one-hour retrospective special.

“Free Radio” (11 p.m., VH1): The comedy about a really awful radio personality with a hit show returns for a second season.