Way back when, people used to wait to see movies until they came out on DVD or watch clips from shows when they were broadcast on YouTube. That’s so 2007. Tonight, CW broadcasts “Dr. Horrible’s Sing-Along Blog” (8 p.m.), an online musical video produced by Joss Whedon and starring Neil Patrick Harris, Nathan Fillion and Felicia Day.

It was viewed a lot or, in Internet-speak, “went viral” sometime in 2008. Reportedly, it has been seen 50 million times since.

So let me get this straight. As part of introducing its new season, the CW is airing a self-consciously cheesy (Neil Patrick Harris’ wheelhouse) Internet musical that’s 4 years old, has already been seen repeatedly by millions of potential viewers and can be screened on demand at any given moment. And this is supposed to give the network some kind of hip credibility? For the record: I don’t get it.

l The more television changes, the more it stays the same. An old chestnut is the candid-camera prank show. Tonight, Lifetime launches “Prank My Mom” (9 p.m.). Vivica A. Fox hosts.

On “Mom,” children test their acting (don’t call it lying) ability as they do outrageous things in the presence of dear old Mom just to get a rise of out her and see how far they can push her buttons. In one setup, a young man shoplifts and gets caught, right in front of his mortified mother. In another, a not-so-dutiful daughter sets her mother up on a painfully embarrassing blind date.

Tonight’s other highlights

• A social worker pays a visit on “Raising Hope” (7 p.m., Fox).

• Yet another quaint local festival on “Hart of Dixie” (7 p.m., CW).

• “History Detectives” (7 p.m., PBS) evaluates a poster from World War I.

• Rolling out the welcome wagon on “New Girl” (8 p.m., Fox).

• “Frontline” (8 p.m., PBS) airs “The Choice,” profiling President Barack Obama and challenger Mitt Romney.

• James Franco and Marina Abramovic form a mutual admiration society on the sixth season premiere of “Iconoclasts” (7 p.m., Sundance).

• Danny makes a professional commitment on “The Mindy Project” (8:30 p.m., Fox).

• Mia’s dad arrives on “Vegas” (9 p.m., CBS).

• Kristina breaks big news on “Parenthood” (9 p.m., NBC).