On Friday afternoon, “The Fresh Beat Band” (Nickelodeon at 1 p.m.) features an hour-long special, “The Wizard of Song,” in which guest star Jason Mraz plays the wizard and performs.

After hanging on for five seasons, ratings-challenged “Chuck” (NBC at 8, 9) finally says goodbye with a two-part episode. In the first hour, Sarah keeps a huge secret from Chuck to protect him, and Ellie and Awesome mull a decision that could change their lives. And in the series finale, Chuck enlists the gang to stop his enemy from destroying everything he’s worked for over the past five years.

Wondering how that product that attempts to potty-train cats from Season 2 of “Shark Tank” (ABC at 8) worked out? You’re in luck — the show provides an update and features a new future entrepreneur who wants to launch a cat-drawing service.

Tony Bennett partners with lots of singers on “Great Performances — Tony Bennett: Duets II” (MPT at 9), including Lady Gaga, Michael Buble, Aretha Franklin and Willie Nelson. The show also features Bennett singing “Body and Soul” with Amy Winehouse.

One crew member quits at Quartz Creek on “Gold Rush” (Discovery at 9), and Parker starts to have thoughts about his future.

After hanging on for five seasons, ratings-challenged “Chuck,” starring Zachary Levi as the title character, finally says goodbye with a two-part episode. (Chris Haston/NBC)

The team tracks a mysterious girl who can predict death on “Fringe” (Fox at 9), and Olivia tries to figure out the scary warning from the Observer.

“Bering Sea Gold” (Discovery at 10), a new docu-series that chronicles the adventures of people searching for gold at the bottom of the sea in Nome, Alaska, is reviewed by Hank Stuever on Page C1.

First, there was “Spartacus: Blood and Sand.” Then, the prequel, “Spartacus: Gods of the Arena.” Now, “Spartacus: Vengeance” (Starz at 10) picks up where the first season left off, as the gladiators continue to rebel. Liam McIntyre takes over in the title role. Tragedy struck last year when Andy Whitfield, the original lead, died at 39 from non-Hodgkin’s lymphoma.

Journalist Martin Bashir, satirist Kennedy and Rep. Dana Rohrabacher (R-Calif.) make up the panel on “Real Time With Bill Maher” (HBO at 10); chef Mario Batali and former representative Mark Foley (R-Fla.) are interview guests.

Emily Yahr