Torchwood (BBC, 2006)

Episode: Children of the Earth (Day 3)

Airdate: July 28, 2009

Children around the world point toward London, and the lads and lasses in London point to the centre of the city. The 456 open the clouds, announce their arrival ("We are here"), and travel down a pillar of fire coming from the sky. How do you top an entrance like that? Demand 10% of the world's children.

Battlestar Galactica (Sci Fi, 2005)

Episode: Lay Down Your Burdens (Part 2)

Airdate: March 10, 2006

Okay, so the Cylons weren't exactly aliens, but they pulled off not one, but two mind-blowing surprise attacks on the human race. After they annihilated most of mankind, the Cylons decided they wanted to dominate their makers -- at least those who were left.

Threshold (CBS, 2005)

Episode: Trees Made of Glass

Airdate: September 16, 2005

Navy officers at sea climbed on deck to see a four-dimensional sphere continuously changing shape in the sky above them. The sphere didn't just emit a mesmerizing glow, it caused nosebleeds and felled most of the crew. A few people weren't horribly disfigured or killed, and they evolved to a higher level of intelligence, becoming part of the alien race.

Invasion (ABC, 2005)

Episode: Pilot

Airdate: September 1, 2005

A violent hurricane in Florida provided cover for colorful lights to shoot into the water and bond with humans to create sleeper human-alien hybrids. The storm was just the beginning, as the townspeople started to lose memories and act weirder as their alien halves took over.

Smallville (WB/CW, 2001)

Episode: Pilot

Airdate: October 16, 2001

An intense meteor shower pretty much took out the town of Smallville, killing Lana Lang's parents and razing off Lex Luthor's hair. The most important part of the meteor shower was the alien himself, a naked baby named Kal-El who happened upon a kind-hearted couple who will become his foster parents.

The X-Files (FOX, 1993)

Episode: One Son

Airdate: February 14, 1999

Members of the Syndicate gathered their families to prepare for what they thought was alien salvation. Instead, the terrifying alien rebel race -- whose members had blinded themselves to prevent the black-oil virus from taking over their eyes -- arrived with torches and wiped out the seemingly all-powerful Syndicate in one fell swoop.

3rd Rock from the Sun (NBC, 1996)

Episode: Brains and Eggs

Airdate: January 9, 1996

Dick, Sally, Harry and Tommy arrived on our "third-rate planet" in the fictional city of Rutherford, Ohio via a red convertible Rambler. While listening to talk radio in the car, Harry and his extraterrestrial elite team quickly find a few quirks of the human body -- heads that don't rotate, faces with three holes in the front, and boobs that sweat.

ALF (NBC, 1986)

Episode: A.L.F.

Airdate: September 22, 1986

ALF left his planet Melmac because it exploded, and once he was near Earth he followed the shortwave-radio signals of Willie Tanner (a.k.a. K726XAA), causing his spaceship to crash into the Tanner garage. Willie said it best after getting his first glimpse of ALF: "We...we have a visitor."

Mork & Mindy (ABC, 1978)

Episode: Pilot

Airdate: September 14, 1978

Traveling in a large egg-shaped spaceship, Mork was sent from Ork to our "insignificant planet" to learn about primitive societies. After touching down, he broke out of his egg, found his one piece of luggage -- the rest of his luggage got lost along the way -- and met his future wife, an abandoned and distraught Mindy.

My Favorite Martian (CBS, 1963)

Episode: Pilot

Airdate: September 29, 1963

A Professor of Anthropology from Mars was on one of his many missions to Earth, but this time the Air Force's X-15 nearly ran into his spaceship in mid-air. He strained his ship to get out of the way and eventually crashed to the ground, where Tim O'Hara, a reporter for the Los Angeles Sun, rescued him...adopting him as Uncle Martin.