“This is a lot like Back to the Future Part II!”

It’s almost the most honest line in Happy Death Day 2U — admitting that it yet again bogarts the back catalog, asserting its heroine could still stand to watch more movies and acknowledging most of its target audience — born a decade-and-a-half after Marty McFly’s adventures in 2015 — will greet the line with a shrug  … as they did the OG’s Groundhog Day quips.

That passage might look familiar. So does the shiftless start to this sequel, which seems content early on  to let a pivot into full-blown science-fiction rest as a creative raison d’etre. (Its real provenance? A $100-million profit margin) Once Happy Death Day 2U: Into the Death-Verse pivots into a “quantum cyclic dimension” or whatever, it resembles the drive-thru value-meal version of Fringe and The Good Place in its goofiest and most modestly entertaining moments.

In the first film, snotty Bayfield University sorority girl Tree (Jessica Rothe) was slain on her birthday, respawning and retaining knowledge until she could identify and defeat her masked killer. Did this fat-shaming, home-wrecking mope become a better person? Not really, but she gymnastically kicked her killer out a window real nice.

Returning director Christopher Landon also takes sole credit on the script, explaining Tree’s travails as merely a science experiment gone wrong. Ryan (Phi Vu) — the roommate to Tree’s new boyfriend, Carter (Israel Broussard) — tries to “slow time at a molecular level” with a quantum mechanics reactor named Sisyphus. Bayfield’s STEM program? Unexpectedly robust. Its rhetoric department? In trouble if its students slap “Sisyphus” on a gadget meant to succeed.

Anyway, Sisyphus was successful … in creating Tree’s time loop, and now it has ensnared Ryan as well. (At the outset, it is his death day that repeats.) Through a few surprises — fried in a familiar way but still like that unexpected bonus onion ring in your bag — Tree again finds herself reliving, and respawning, on her birthday. “This sucks the biggest mega-balls in the history of ball-suckery!” Tree yells. Again, the rhetoric courses!

Only this time, Tree is in an alternate dimension — one where Carter is not her guy, her supposed BFF Lori (Ruby Modine) doesn’t want her dead and … well, it’s a low-budget Blumhouse jam, so it’s not like our overlords are now talking sharks or anything. There is still an unknown killer in a Bayfield Babies mascot mask whose spree Tree must stop.

But unlike before, Tree faces legitimate dilemmas; let’s just say the new dimension has some definite pros in its favor. You’ve seen these quandaries before and better, but Landon generally course-corrects with conviction. Just forget his credit cookie, which teases an even crazier threequel loop-de-loop before caving for a feckless final image of petty, mean-spirited cruelty.

2U never scrapes the heights of existential horror or hilarity of Netflix’s similarly plotted Russian Doll, but it passably understands ways in which Tree’s pain and losses shaped her and how irreversibly haunted she would be by choosing the easy way out. Overall, Landon more or less rehabilitates her rottenness from the first film and lets Rothe find a mode beyond, say, Goofy Mugging Blonde in Air Bud 18: Lacrossing the Line.

Landon also lets a story about responsibility and reconciliation pivot into a third-act heist plot about putting one over on a cat-fancying dean (played by Steve Zissis). In other words, the filmmaker understands the manner in which unexpected success gives you the leeway to have some frivolous sequel fun. “Every day is a chance to be better,” someone says. It’s taken out of the oven too soon, but at least that notion has been baked into the movie this time.