250 episodes match Down to Earth

Alien encounter buffs gather at a national convention where someone shows up with what appears to be a piece of an alien spaceship.

Mystery!? Little Earth - Middle Earth - Big Earth (怪！？小地球・中地球・大地球, Kai!? Shōchikyū Chūchikyū Daichikyū) (Original Airdate: April 6, 1974)

As the city waits impatiently for another visit from "Batman," Alice continues to taunt Kate with a secret. Meanwhile, a friend of Bruce Wayne visits Kate. (imdb)

Valery creates a detailed plan to decontaminate Chernobyl; Lyudmilla ignores warnings about her firefighter husband's contamination.

The Doctor and Rose arrive on New Earth and meet old friends and enemies in a hospital which can cure every disease. But the cures come at a terrible cost. (imdb)

In a South Yorkshire city, Ryan Sinclair, Yasmin Khan and Graham O'Brien are about to have their lives changed forever, as a mysterious woman, unable to remember her own name, falls from the night sky. (imdb)

When a drill drills to deep into the earth, something that had been hibernating beneath the earth's crust is woken, and it's hungry for revenge. (imdb)

The return of an old enemy leaves Earth along with 26 other planets stolen from their places. As the Doctor and Donna look for the whereabouts of Earth, former companions of the Doctor assemble a resistance against the new Dalek Empire. (imdb)

Morgan continues his search for Carol. Meanwhile, Rick and the group travel to the Hilltop with an ailing Maggie, leading to a daunting and life-changing confrontation.

When Ego and a young Peter Quill attack Earth in 1988, Howard Stark and Peggy Carter form a team. (imdb)

The gang comes together for Barry and Iris's wedding, but the ceremony is crashed by villains from Earth-X. (imdb)

Harrison, Cisco and Barry travel to Earth-2 to save Harrison's daughter. Barry assumes the role of his doppelganger, who's married to Iris. He then encounters alternate-Caitlin and alternate-Ronnie, who are Zoom's agents. (imdb)

On Earth-2, the team asks for help from an unexpected source to find Zoom's lair, while on Earth-1, Caitlin tries to perfect Velocity-9 so Jay can stop the Geomancer. (imdb)

The gang comes together for Barry and Iris's wedding, but the ceremony is crashed by villains from Earth-X. (imdb)

Supergirl and the DEO are assigned to protect the President when an attack on her causes alien vs. human rights in National City to heat up. Alex investigates the case with Maggie Sawyer while Kara fears Mon-El may be responsible. (imdb)

It's the winter formal at East Highland. (imdb)

The gang comes together for Barry and Iris's wedding, but the ceremony is crashed by villains from Earth-X. (imdb)

Forced to live "off of the land" on Earth Day, tension within the group erupts as treatment intensifies and hunger pains set in. (imdb)

Finally reunited, Burnham and the U.S.S. Discovery crew journey to Earth, eager to learn what happened to the Federation in their absence. (imdb)

Discovering that Jasper may still be alive, Clarke, Bellamy, Finn, Wells and Murphy head out to find him. On the Ark, Abby is determined to prove Earth is habitable, and enlists a mechanic to craft an escape pod. (imdb)