‘Death Day 2U’ goes ‘Back to the Future’

Living the same day over and over can get pretty monotonous – or terrifying, if you’ve got somebody in a baby mask knifing you constantly.

Wait a minute, that’s what we wrote a year and a half ago about how “Happy Death Day,” the hit rom-com horror comedy, follows the “Groundhog Day” template. But knowing that is only half the battle in the sequel “Happy Death Day 2U,” which hit theaters Wednesday. It has a Marty McFly in the ointment.

True, the follow-up still has shades of Bill Murray’s classic “Groundhog,” since college student Tree Gelbman (Jessica Rothe) is forced to again keep reliving her birthday over and over again while a knife-wielding psycho wearing a cherubic Bayfield Babies mask is on the loose.

This time, though, director Christopher Landon has introduced a “Back to the Future” sci-fi element that explains the movie’s core conceit and adds the wrinkle of parallel dimensions.

Hey, even the same character who referenced “Groundhog Day” in the first “Happy Death Day” makes mention of “Back to the Future II” in the sequel.

Here are five things that make “2U” the next best thing to a return trip in the DeLorean:

A new Doc Brown, only younger

Ryan (Phi Vu), dormmate to Tree’s love interest Carter (Israel Broussard), is a main character in the sequel because his quantum mechanics thesis project has a pesky tendency of creating time loops when activated.

The timeline needs to be fixed

“2U” picks up where the first “Death Day” left off but quickly negates the happy ending and puts Tree back in the hated time loop. (Her raging at the realization is a highlight.) Yet, like Marty finding out he needs to have his parents meet in the 1950s in “Back to the Future,” Tree discovers certain things and people have changed this time around.

Tree’s deaths have a purpose

The first film had its main character navigate instances of being murdered again and again so she could figure out the killer. That gets a tweak in “2U”: Fixing the time loop means she has to kill herself a bunch of times. Unfortunately, as in “Happy Death Day,” every death takes a toll on Tree’s body.

Hard decisions need to be made.

With shades of “Back to the Future III,” where Doc Brown is in love in the Old West and unsure of returning to the present, Tree has to weigh which timeline she wants to be in, since it means choosing between loved ones.

Don’t forget the baby mask killer

While “Happy Death Day” gleefully mashes up more genres and inspirations, its signature villain still lurks at the heart of the franchise.

Tree (Jessica Rothe) faces another time loop of a day. UNIVERSAL PICTURES