The “candid camera” ethics reality series “Primetime: What Would You Do?” (8 p.m., ABC) returns for a full season of new episodes. Tonight’s premiere arrives with three rather loaded situations. But I guess that’s the point.

The first involves the case of a cougar tutor, a 30-something woman at a coffee shop who is supposed to be helping a teenaged boy with his homework, but whose provocative dress and come-hither attitude seems to distract him from his periodic tables. What’s a diner to do?

In another case, inspired by recent headlines, folks are subjected to a scene of a crowd taunting a young man because he’s gay. Will they intervene or simply walk away? The third scenario seems the most controversial. Actors pretending to be protesters against the war in Afghanistan heckle a man attempting to volunteer for the service at a recruiting office.

• On a similar front, “20/20” (9 p.m., ABC) devotes an hour to the problem of young people and heroin addiction. According to the Substance Abuse and Mental Health Services Administration, the number of heroin addicts has doubled since 2007. And the problem transcends race, class and neighborhoods, with many suburban children from prosperous homes falling for the drug.

• “Dean of Invention” (9 p.m., Planet Green) examines the notion of the “Wired Brain,” or brain-computer interface that will enable people to fly and drive without using their hands, and perhaps even give speech back to those who have lost their voice.

• Linus lures Sally away from a Halloween party to share a special event amongst the gourds in the 1966 special “It’s the Great Pumpkin, Charlie Brown” (7 p.m., ABC), airing for the second night in a row and still getting good ratings after 44 years.

To get a notion of the vintage nature of this holiday favorite, the action on the just completed season of “Mad Men” takes place at roughly the same time this cartoon was created. To look at it another way, we are as far removed in time from 1966 as ’66 was from 1922, just a couple of years after the events on “Boardwalk Empire.” Some things change, but others endure. “The Great Pumpkin” may never make it to Linus’ patch, but he’s never far from our hearts.

What programming produced today will still have an audience, or any entertainment value, in the year 2056? Too many of our most popular series have an ephemeral, throw-away quality. Does anyone watch “Dancing with the Stars,” “American Idol” or “Jersey Shore” more than once? In contrast, series like “I Love Lucy” and even “Law & Order” still find viewers decades after their creation. There’s a crucial difference between programs that have residual value and those that do not. Broadcasters forget that at their peril.

Tonight’s other highlights

• Allison feels powerless to prevent a catastrophe foreseen on “Medium” (7 p.m., CBS).

• A Tennessee school picks up the pieces after a deadly flood on “School Pride” (7 p.m., NBC).

• Death on a rooftop on “CSI: NY” (8 p.m., CBS).

• Our heroes stumble upon a vast conspiracy way above their pay grade on “The Good Guys” (8 p.m., Fox).

• A police informant (Johnny Depp) gains the confidence of mob boss (Al Pacino) in the 1997 drama “Donnie Brasco” (8:40 p.m., Encore), based on a true story.