What TV shows will be remembered and cherished a generation from now? It’s never as obvious as you think. The most-watched shows of one era are often forgotten when their time passes, while fringe shows – particularly those adored by young audiences – become cultural touchstones.

Back in the early 1970s, “The Sonny & Cher Comedy Hour” topped the ratings. A photo of Cher on the cover of Time magazine boosted it to best-seller status. But now that series seems like a polyester relic. “The Brady Bunch” never cracked the top 30 in ratings but remains a beloved memory to several generations of young viewers.

With that model in mind, it’s safe to assume that memories of “The Ghost Whisperer” will trail off into the ether, while the cartoonlike “Hannah Montana” (6 p.m., Disney) continues to generate nostalgia well into the new century.

For the uninitiated, Miley Cyrus stars as high school freshman Miley Stewart, who also happens to be the teenage singing sensation Hannah Montana. Miley’s real-life father, Billy Ray Cyrus, stars as her father, a country star looking after his daughter’s career.

For all of her superstardom, Miley’s life is dominated by a normal post-adolescent blend of anxiety and shenanigans. In tonight’s episode, the second-season opener, Hannah’s taste for audience-pleasing encores puts a strain on Miley’s throat. She submits to a week of silence and even faces surgery to save Hannah’s voice and career.

Disney follows “Hannah” with another serving of the feature-length “High School Musical” (7 p.m., Disney). For people 16 or older, it’s easy to overlook both “Hannah” and “Musical” and not even notice how “Musical” became one of the runaway pop sensations of 2006. The last time I checked, its soundtrack remained the highest-selling CD of the year.

¢ Viewers of a slightly older vintage can catch dance-driven musicals that defined their times. John Travolta stars as a directionless hardware-store clerk whose passion and footwork turn him into the king of his Brooklyn disco in the 1977 hit “Saturday Night Fever” (7 p.m., AMC). The soundtrack album from this film was so popular that it was estimated that one in 10 Americans owned a copy of the double-LP.

Ten years later, in 1987, America developed a fever for “Dirty Dancing” (6:15, TMC), a nostalgic glance back at dancing with the help at a Catskills summer resort in the summer of 1963. Patrick Swayze stars as the hot teacher who teaches a sheltered teen (Jennifer Grey) how to move, much to the chagrin of her protective father (Jerry Orbach, “Law & Order”).

Tonight’s other highlights

¢ Jamie Foxx won a best-actor Oscar for his portrayal of musical innovator Ray Charles in the 2004 biography “Ray” (6:30 p.m., FX).

¢ A botched experiment leaves Carter stranded in a shadow zone on “Stargate SG-1” (7 p.m., Sci Fi).

¢ Scheduled on “20/20” (9 p.m., ABC): Gender-confusion issues begin in grade school.

¢ Adrian attends a rock concert on “Monk” (9 p.m., USA).