You might not think to pop in a science fiction movie or TV episode when you're looking for a good bawl. And you'd be wrong. Here are 15 surefire ways to get the tear ducts leaking.

Tearjerkers are like the filmed-entertainment equivalent of the Blues: You put them on to see someone else who's life predicaments are worse than yours. Usually involving people with better hair and makeup. But if you're looking for a good weepie that also has lasers and/or time-travel, here are a few good places to start:

Brad Bird's animated opus is the frickin' granddaddy of unexpected bawl yankers. You sit there, strapped in for some retro-sweet boy-and-his-robot action when, suddenly, you get to the end...and there's guns and jets and nukes and heroism and sacrifice and tears. Lots of tears.

Jeff Bridges was at his downy-softest playing an alien who comes to Earth and takes the form of Karen Allen's dead husband. Her conflicting emotions, his disillusion with a planet he thought would be welcoming, the authorities' desire to do really bad things to the Starman — all of that combines to form John Carpenter's most emotionally mature film ever.

Seriously, if you didn't well up when — after Wall*E put his life on the line to help Eve locate Earth — the frantic Eve races to his old trailer-home and repairs him with a lightning speed only the desperately in love have and Wall*E comes back online...wrong....

J-Just give me a minute.

LOST: "The Constant"
Easily, the most affecting episode of this mystery-box of a show. When poor Desmond Hume (Henry Ian Cusick) finally gets to talk to the woman he's waited years and years to reconnect with — and suffered the slings and arrows of electromagnetic fortune — it plays like a validation of all the time we've devoted to Lost.

It should've been the series finale. Sure, that would've meant we'd never have gotten "Once More With Feeling" or Evil Willow or the Slayer Army, but Buffy sacrificing herself to protect her friends, her sister-who-wasn't, this plane of existence was heartrendingly perfect.

"I'll be" Nuff said.

This 1968 adaptation of Daniel Keyes' Flowers for Algernon finds Cliff Robertson playing the title character, a man of severely limited intelligence who undergoes an experiment procedure that makes him through-the-roof brilliant. The fateful hammer that falls on Charly is devastating, all the more so because — thanks to that experiment — he can see it coming.

When he made the unremarkable 1976 version, producer Dino di Laurentiis apocryphally said to a reporter, "Everybody cry when monkey die." It was as true for Peter Jackson as it was for Dino: When a confused Kong is atop the Empire State Building, defending a turf he doesn't recognize from an enemy he doesn't understand — all for the love of a teensy blonde — you can't help but feel for the guy.

STAR TREK: "City on the Edge of Forever"
You will believe a Kirk can cry. When the good Captain and his first officer get stuck in the Great Depression-era New York City, chasing a drug-maddened Dr. McCoy, they realize that in order to save the future's timeline, they're going to have to allow someone to die. And, Kirk being Kirk, he falls in love with that someone first.

While I will go on the record and say that the thing that happens to Wash is more shocking than tearjerking, but I can respect those who got all broken up about it. So here, my fellow Browncoats: a shiny bone.

Tim Burton's dewy-misfit fixation never found a better outlet than this, his first collaboration with Johnny Depp. Come to think of it, Depp's beautiful, pale, wild-maned high-school outsider is like the proto-Edward Cullen. But with finger-knives instead of fangs.

DOCTOR WHO: "Father's Day"
Personally, I wasn't a fan of the BBC update of this venerable sci-fi classic — until I saw this episode, in which Rose Tyler (Billie Piper) traveled back to the day her father died. Against the warnings of the temporal veteran the Doctor (Christopher Eccleston), she saved her dad's life...and doomed London in the process. Sometimes we want what we cannot have.

Berlin is full of angels, members of the heavenly host that watch over the people of the great German city: listening, observing, recording. But they never interfere until one, Damiel (Bruno Ganz), falls in love with a human and leaves his angelic life behind. Wim Wenders' 1987 film is both hauntingly beautiful and infinitely better than the mopey Nicolas Cage-Meg Ryan remake, City of Angels.

Speaking of James T. Kirk crying — SPOILER ALERT IF YOU DON'T HAVE PUBES OR HAVE BEEN LIVING IN A BUNKER FOR THE PAST 20 YEARS — Spock's death was enough to send the old man into a blubbery frenzy in the antimatter chamber. But it was Kirk's eulogy at Spock's funeral that hammers it home: "Of all the souls I've encountered in my travels, his was the most...human." And then Scotty's bagpipe "Amazing Grace" and the Kleenex.

DOCTOR WHO: "Doomsday"
And, finally, in case your face isn't all watery yet...the goodbye.