Hollywood loves a bandwagon. If something’s hot, you can bet others will jump onboard.

But the piggybacking is reaching wacky levels of late.

Take the two-disc collector’s edition of “The Poseidon Adventure,” being released by Fox on May 9. Disc is timed to coincide with the bigscreen redo of “Poseidon,” which hits theaters May 12.

Thing is, Wolfgang Petersen‘s big-budget remake is a Warner Bros. release — not 20th Century Fox’s.

Such tie-ins are a no-brainer: What could be more rewarding than piggybacking on a release by the competish, and all that P&A coin they’re spending?

Indeed, last November, Warner Bros. released a special DVD of the 1933 “King Kong” just before Universal’s “King Kong” remake, directed by Peter Jackson, hit theaters.

But turnabout is fair play, and there’s a frenzy of tie-ins timed to U’s DVD of the “Kong” redo.

Fox will bow a “Planet of the Apes Ultimate DVD Collection.” Sony has a “Godzilla Monster Edition,” featuring its 1998 remake and episodes from “Godzilla: The Series.” And Warner will re-release its 1933 “Kong” DVD again, minus a special seven-part docu directed by — yes, that’s right — Peter Jackson.

Then there’s the curious case of Fox’s Johnny Cash biopic “Walk the Line,” which hit DVD on Feb. 28.

Next week, Columbia/Sony will release a special edition of its “I Walk the Line,” the 1972 John Frankenheimer pic starring Gregory Peck as a sheriff who falls in love with a younger woman, played by Tuesday Weld. Box art and stickers prominently tout its inclusion of music by — Johnny Cash.