Two and a Half Men 9 p.m., Channel 4
We’ve all been very concerned about the fate of this fine comedy, ever since Charlie Sheen deconstructed himself out of prime time. What would happen to the delicate mix of character comedy and social satire when Sheen, a master of subtle humor, was out of the mix? Would this tower of network greatness fall? Would TV lose its pinnacle of wit? Well now we know we can relax, because the masterful Ashton Kutcher (pictured) is on the case, joining the show tonight as a brokenhearted billionaire. Surely he will save the day.
How I Met Your Mother 8 and 8:30 p.m., Channel 4
At some point a year or two ago, I realized that “How I Met Your Mother’’ had gone irrevocably downhill, that it was retreading over old territory, and that I would nonetheless watch the show until the very end. I still like the characters, and I still want to see Ted meet the mother. The series returns tonight for season 7, with Barney’s mystery wedding and, in a second episode, with Marshall getting his dream job. Guests this season include Kal Penn as Robin’s shrink and Martin Short as Marshall’s boss. Pictured: Josh Radnor as Ted.
The Roast of Charlie Sheen 10 p.m., Comedy Central
With TMZ gravy.
Dancing With the Stars 8 p.m., Channel 5
Nancy Grace? Can one dance bombastically?
The Sing-Off 8 p.m., Channel 7