"The Big Bang Theory" (8 p.m., CBS, TV-PG) says goodbye with an hourlong episode, followed by "Unraveling the Mystery: A Big Bang Farewell" (9:30 p.m., CBS, TV-14), featuring cast and creators in retrospective mode.

The cast, including Johnny Galecki, Jim Parsons, Kaley Cuoco, Simon Helberg, Kunal Nayyar, Mayim Bialik and Melissa Rauch will also appear on "The Late Show With Stephen Colbert" (11:35 p.m., CBS).

Whenever a popular comedy signs off, folks wonder if there will ever be another sitcom capable of attracting a broad audience.

The end of "Big Bang" is a good time to appreciate its writer and creator, Chuck Lorre, and his ability to go against prevailing trends. At a time when many TV critics, including this one, saw the future of TV comedy as single-camera documentary-style fare like "The Office," Lorre offered viewers "Two and A Half Men," "Big Bang," "Mike & Molly" and "Mom," traditional multi-camera sitcoms with conversations punctuated by punch lines and occasional hugs.

Earlier, when comedies like "Seinfeld" heralded an era of young urbanites whose strongest relationships were their "Friends," Lorre put the accent on family ties.

His work on "Roseanne," "Cybill," "Dharma and Greg" and "Grace Under Fire" emphasized the relationship between less-than-perfect parents and their children, which continued on "Two and a Half," "Big Bang" and, most notably, "Mom."

Sheldon (Jim Parsons) on "Big Bang" had such a strong connection with his mother that it became the basis for the spin-off "Young Sheldon." Wolowitz's mother was heard and not seen. But when actress Carol Ann Susi, who provided her voice, died in 2014, sadness prevailed among the show's fans.

"Big Bang" was a broadly popular show with an emotional, almost cultlike connection to its audience. That's a rare feat, difficult to replicate, and worth appreciating.

- Time was, starring on a TV show was a dream come true. Things have changed. This year, we've seen Damon Wayans try to talk his way off the cast of the just-canceled "Lethal Weapon," while Jussie Smollett found an interesting way to get written off "Empire."

Just last week, Constance Wu seemed to lament the fact that her sitcom "Fresh off the Boat" had been renewed. After her role in the 2018 smash "Crazy Rich Asians" (8 p.m., HBO), it appears she has better things to do.

Tonight's season finales

- A fog obscures events on "Grey's Anatomy" (8 p.m., ABC, TV-14).

- Sheldon throws a Nobel Prize party on "Young Sheldon" (9 p.m., CBS, TV-PG).

- A wildfire on "Station 19" (9 p.m., ABC, TV-14).

- A radical militia on "S.W.A.T." (10 p.m., CBS, TV-14).

- A drowning death on "Law & Order: Special Victims Unit" (10 p.m., NBC, TV-14).

- Voters feel intimidated at the polls on "For the People" (10 p.m., ABC, TV-14).

- Sam takes a breather on "Better Things" (10 p.m., FX, TV-MA).

Tonight's other highlight

- Death undoes a dancing duo on "iZombie" (8 p.m., CW, TV-14).

Series notes

On two helpings of "Superstore" (NBC, TV-14), sabotage (8 p.m.), divide and conquer (8:30 p.m.) ... Things get frisky on "Paradise Hotel" (8 p.m., Fox, TV-14).

On two helpings of "Brooklyn Nine-Nine" (NBC, TV-14), a serial killer (9 p.m.), strange bedfellows (9:30 p.m.) ... Murphy feels rattled on "In the Dark" (9 p.m., CW, TV-14).

Late night

"The Daily Show With Trevor Noah" (11 p.m., Comedy Central) looks at young people involved in politics ... Judd Apatow and Rachel Feinstein appear on "Conan" (11 p.m., TBS, r, TV-14) ... The cast of "The Big Bang Theory" and the Barenaked Ladies are booked on "The Late Show With Stephen Colbert" (11:35 p.m., CBS) ... Jimmy Fallon welcomes Jessica Alba, Yara Shahidi and The Head and the Heart on "The Tonight Show" (11:35 p.m., NBC) ... Trevor Noah, Billie Lourd and Ciara appear on "Jimmy Kimmel Live" (11:35 p.m., ABC).

Aidy Bryant, John Waters, Sen. Michael Bennet and Johnny Radelat visit "Late Night With Seth Meyers" (12:35 a.m., NBC) ... Halle Berry, Anjelica Huston and Allison Williams appear on "The Late Late Show With James Corden" (12:35 a.m., CBS).

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