Captivated by the multiverse and alternate realities? Here’s a handy guide to some good stuff

— “It’s a Wonderful Life” (1946): In this Christmas classic, family man George Bailey grows increasingly frustrated as opportunities pass him by, and it takes an angel-in-training — on Christmas Eve — to dump him into a universe where he never existed and show him how important his life is.

— “Doctor Strange in the Multiverse of Madness” (2022): After years of hints and slivers, including an emerging plotline in “Spider-Man: No Way Home” (2021), Marvel goes full-on multiverse in this exploration of how realities can collide and start bleeding into each other.

— “Sliding Doors” (1998): Gwyneth Paltrow misses a train — and doesn’t. The two splinter realities unfold very differently, producing versions of her character that must be reconciled.

— “Yesterday” (2019): Jack Malik, aspiring musician, finds himself stranded in a near-identical universe where no one has ever heard of the Beatles (or Coca-Cola, for that matter). He starts singing the songs as if he wrote them. Hijinks and big feels ensue.

— “The Butterfly Effect” (2004): Ashton Kutcher plays a college student who finds he can revisit his past and change things, and each time he does so a different reality is born.

— “The Family Man” (2000): After an encounter in a convenience store, arrogant Manhattan finance guy Jack Campbell wakes up in a very different — and less affluent — life in the New Jersey suburbs and finds himself married to and parenting with his old girlfriend, whom he had walked away from years ago. As he navigates his new life and the choices he made or didn’t make to get there, a more complex picture emerges.

— “Shrek Forever After” (2010): Shrek finds himself in an alternate, darker reality where he never got together with Fiona.

— “Star Trek” (1967 and beyond): A “mirror universe” reveals a darker, more evil version of the show’s United Federation of Planets — the Terran Empire, punctuated by cruelty and assassination. This universe was revisited in multiple “Trek” sequels in the 1990s and 2010s.

— “Russian Doll” (2019-present): In season one, Nadia keeps dying at a party and keeps waking up in slightly different universes, though each awakening always ends with her death.

— “Undone” (2019-2022): In this striking hybrid of live action and animation, a young woman’s relationship with her long-dead father takes an unexpected turn after a car accident, when he shows up in a vision and tells her other realities are possible — including one in which he was alive and around for her upbringing.

— “Fringe” (2008-2013): Sci-fi meets family drama meets law-enforcement procedural as a father makes an incursion into a parallel universe to save — and steal — another version of his son and deals with the world-changing consequences.

— “The Man in the High Castle” (2015-2019): It’s the 1960s, the Nazis and Japan won World War II and the world is playing out very differently — in sometimes unexpected ways.

— “For All Mankind” (2019-present): The Soviets won the space race and got to the moon first. This is how history played out afterward.

— “Flashpoint” (2011): The DC Comics series that informed “The Flash” movie, it addresses the damage that the main character, Barry Allen, does when he goes back in time to save his mother.

— “What If?” (1970s on): This speculative series, which started in the comics and moved to streaming TV in 2021, takes different corners of Marvel’s “main” universe and remixes events and characters.

— “House of M” (2005): The Scarlet Witch reboots reality and changes the lives of some of Marvel’s top heroes in fundamental and chaotic ways, including Spider-Man, Doctor Strange and Captain America. This series was one of the ingredients of the 2020 Marvel TV show “WandaVision.”

— “The Mirage” (2013): This novel by Matt Ruff, author of “Lovecraft Country,” posits a through-the-looking-glass world where American Christian fundamentalists were the perpetrators of 9/11, attacking the Twin Towers in Baghdad, located in the United Arab States. Characters include remixes of Saddam Hussein and Osama bin Laden.

— “Einstein’s Dreams” (1992): Dreamlike fiction by Alan Lightman that chronicles explorations into different permutations of time and alternate universes that Albert Einstein might have dreamed while coming up with the theory of relativity in 1905.

— “The Space Between Worlds” (2020): A novel by Micaiah Johnson that chronicles a time when travel across the multiverse has become commonplace — which creates very distinct safety problems for some of those who travel.