In at least one episode, time travel happened. Walter met a MIT time-travel researcher (Peter Weller of RoboCop) who, in an effort to change his dead fiance’s past, sucked the biological energy out of a train car of people. It had a great payoff in the end when he sent a message to Walter.
It came from the future! 4400 people (give or take) are abducted from various points in time and all returned to earth circa 2004 with enhanced abilities. One woman returns pregnant and her freaky daughter rapid-ages.
The whole earth simultaneously has a really weird dream about the exact same point in the future. Except it's not really a dream, but more of a case where you can't fight fate, because what happens, happens.
In the fourth season, Felicity is suddenly given a chance (by reasons not explained) to go back in time to redo the Noel/Ben choice and then live with the consequences. Most people hated it, but I loved this storyline. (Mostly because Noel was the best choice.)
This show didn't really move through time, but showed two parallel timelines where one of the title characters grew up to become president, and the other had a far worse outcome. Part of the show took place in the present, and part in the future. They teased the mystery of which brother was the survivor and which was president for a while.
This Blackadder one-off gave the scurrilous Edmund his own time-machine, allowing him to deck William Shakespeare, piss off the Scots army and kill all the dinosaurs with one pair of Baldrick's underpants.
Smallville references the future of Clark as Super-you-know-who quite a bit, and in the superb 200th episode, Brainiac shows Clark a future in which he finally accepts his superpowers and has shared the knowledge of them with Lois.
In this cancelled-too-soon comedy starring an adorable Penn Badgley, an unhappy 34-year-old Joel Larsen is given the opportunity to change to outcome of his life when he is transported back to 1981 and finds himself trapped in his 14 year old body. Trying to rectify past mistakes leads to a lot of really funny moments, including when he spills the ending of "Empire Strikes Back" to some bullies in line to see it.
Considering all the weirdness taking place on this island, surprisingly time travel is not even the most bizarre. In addition to the big jump back to the 1970s taken by half the island survivors, there was the excellent and mind-bending time travel episode "The Constant."
If only we could go back in time to the first season when this show was good. Hiro took a journey back to the days of the Samurai in one storyline, and comic artist Isaac had a knack for drawing the future in his work.
Poor Sam Tyler...is he in a coma, back in time, or dead? Either way, he has to deal with the hard-nosed copper Gene Hunt (one of the best TV characters, ever) and solve cases the old-fashioned way, without modern forensics and computers. He must also deal with those pesky paradoxes when he meets up with his parents and gets involved in their contemporary drama. Oh, and cover your eyes for the scariest TV test card character ever.
In this sequel to Life on Mars, DCI Alex Drake suffers Sam Tyler's fate when she is shot in the head. Except she is returned to the 80s, not the 70s, and she has a daughter to get back to. Luckily (?!) she is also paired with the fabulous Gene Hunt. Another exception is that this show had twice as many series as LoM. Alex also encounters her parents and gets involved in the mystery of their deaths.
Gary Hobson receives tomorrow's newspaper today, with the understanding that he will spend the day saving the life of someone who is about to die in an accident, be executed for a crime they didn't commit or some such.
First, I just have to say that it's downright criminal that this show was only on for 12 episodes. It was way brilliant, cool and funny.
Okay, MM and WW did not travel through time, but Hercules' Kevin Sorbo played a cryogenically frozen superspy who went into the deep freeze in the 60s and was thawed out in 2008. He had a lot to learn about today's techniques and new developments in etiquette.
Can't believe I forgot this one! Dr. Nick Cutter and crew found literal portholes to the past, future and everywhen in between. Sometimes the crew would let nasty dinosaurs and such wreak havoc on our world (next time, bring the army guys with you, k?) and sometimes they would stupidly let themselves get trapped in the distant past.
In a recent episode, one of the show's best, a simple roll of the dice produced seven different timelines (in one the die was not rolled at all) that showed what each of the main characters brought to the group and what happens when they are absent from it. It was truly brilliant and very funny.
Sadly, the darkest timeline is currently in effect, as this show is no longer on NBC's schedule (indefinite hiatus.)