Two years have passed since “Teen Beach Movie,” but just three months of time onscreen. And that offers about as much as anyone needs to know about the sequel, “Teen Beach 2,” which clearly feels no incentive to tamper with success. The only wrinkle, such as it is, involves reversing the first movie’s central conceit, bringing characters from a ’60s beach movie into the present-day real world, instead of vice versa. But all that – and the other plot threads stitched together from various sources – is a pretty thin excuse to reunite the gang to dance and sing again.

To its credit, Disney Channel’s commitment to live-action musicals introduces its audience to a genre that doesn’t gain much exposure elsewhere on TV, so the second-guessing should be kept to a minimum. That said, given that some parents will doubtless be lulled into sitting through these exercises with their kids, it behooves them to make the between-the-music sequences as painless as possible.

That objective isn’t helped by letting the movie run 104 minutes, which results in additional clunky dialogue and exposition to connect the musical numbers generated by a small army of songwriters and producers, and choreographed by Christopher Scott and director Jeffrey Hornaday. While a few of those performances stand out – including a clever one about how much better it is to be in the movies – there’s a semi-numbing sameness to the pop hooks and vocals.

As for the plot, well, beyond the obvious “The Purple Rose of Cairo” riffs (again), “Grease” is the word. Because while surfers Brady (Ross Lynch) and Mack (Maia Mitchell) were brought together by their adventure in the movie “Wet Side Story,” now that summer’s over, they find themselves mismatched now that they’re back in school – her an ambitious overachiever, him a slacker who misses a College Fair. “It’s almost like the school you wants nothing to do with me!” Brady pouts.

Fortunately (or not), fiction intrudes, with the two leads from the movie, Lela (Grace Phipps) and Tanner (Garrett Clayton), stumbling into Brady and Mack’s world. Although the two real kids fret about the possible consequences, the celluloid ones are so dazzled by modern gizmos (among them the smartphone and disembodied voice of Siri) that they’re in no hurry to retreat to their two-dimensional realm, even if it risks falling apart without them.

Everything else is really just the storytelling equivalent of pulling taffy, trying to create enough impediments to keep the narrative clunking along until the next spontaneous outbreak of song. Thankfully, there’s a great deal of talent on the screen, though the words generally sound far better when sung than spoken.

Ever since “High School Musical,” Disney has been enamored with mining this niche, and why not? Not only do the movies garner high ratings, they offer ancillary benefits (including the original music) to feed its merchandising pipeline, and a platform to launch new programs — in this case, a sitcom with its own time-travel twist, “Best Friends Whenever.”

With that in mind, another trip to the beach seems inevitable, although having now explored both sides of this plot, some new wrinkles are probably in order. Pirates? Or dinosaurs? After all, as long as you’re going back in time and pilfering from movies, why not pull out the big guns?

TV Review: ‘Teen Beach 2’

(Movie; Disney Channel, Fri. June 26, 8 p.m.)

  • Production: Filmed in Puerto Rico by Rainforest Prods.
  • Crew: Executive producers, Michelle Manning, David Buelow; producer, Michael O. Gallant; director, Jeffrey Hornaday; writers, Matt Eddy, Bill Eddy; story by Dan Berendsen, Robert Horn; camera, Mark Irwin; production designer, Jennifer Dehghan; editor, David Finfer; choreography, Christopher Scott, Hornaday; music, David Lawrence; songwriters/producers, Mitch Allan, Dan Book, Nikki Leonti, Evan Bogart, Riker Lynch, Rocky Lynch, Ross Lynch,  Ellington Ratliff,  Jens Koerkemeier, Matthew Tishler, Amy Powers, Niclas Molinder, Joacim Persson, Charlie Mason, Johan Alkenas, Twin, Jeannie Lurie, Aris Archontis, Chen Neeman, Faye Greenberg, Adam Schlesinger, Sam Hollander, Josh Edmondson, Charity Daw, S.A.M, Bobby Huff, John Feldmann; casting, Jason La Padura, Natalie Hart, Julie Gale. <strong>104 MIN.</strong>
  • Cast: Ross Lynch, Maia Mitchell, Grace Phipps, Garrett Clayton, John DeLuca, Chrissie Fit, Jordan Fisher, Mollee Gray, Kent Boyd, William T. Loftis, Jessica Lee Keller, Piper Curda, Ross Butler, Raymond Cham Jr.
  • Music By: