Firestar. Originally created for the show Spider-Man and His Amazing Friends when the rights to the Human Torch weren’t available, she was then introduced in Marvel Comics a few years later.
Harley Quinn, written as a minion for Joker on Batman: The Animated Series before she appeared in the comic books
Batgirl, created for the 1960’s TV series, and then appeared in the comics.
Ens. Ro Laren, from ST:TNG and later series, a Bajoran largely raised in refugee camps who eventually joined Starfleet
Kahlee Sanders was a major character in four Mass Effect novels before making her in-game debut at Grissom Academy in Mass Effect 3.
Ursula, Phoebe Buffay’s twin sister (both played by Lisa Kudrow), who was a recurring character on Mad About You before making cameos on Friends
Ambessa and Mel Medarda from the Arcane: League of Legends Netflix series were later added to League of Legends as playable Champions.
Scrappy-Doo, introduced to Scooby-Doo when the show was sinking, 10 years into its run. He later appeared in several other Scooby-Doo series and films.
Morph, introduced in the pilot of X-Men: The Animated Series to be killed off permanently, was later introduced into X-Men and other Marvel comic books, and even resurrected for the revival animated series X-Men '97.
The US version of Godzilla from the 1998 movie became a part of the Japanese franchise in the 2004 movie Godzilla: Final Wars. He was given the name Zilla and was a kaiju but not THE Godzilla.
Grand Admiral Thrawn was originally introduced in a fantastic trilogy of novels by Timothy Zahn before being incorporated into Star Wars canon in The Clone Wars animated TV show. He made his live-action debut in Ahsoka after brief mention in The Mandalorian.
Ellery Queen’s secretary Nicky Porter started out on the radio show but was then incorporated in two of the novels as well as the short stories.
Firestar. Originally created for the show Spider-Man and His Amazing Friends when the rights to the Human Torch weren’t available, she was then introduced in Marvel Comics a few years later.
Harley Quinn, written as a minion for Joker on Batman: The Animated Series before she appeared in the comic books
Batgirl, created for the 1960’s TV series, and then appeared in the comics.
Ens. Ro Laren, from ST:TNG and later series, a Bajoran largely raised in refugee camps who eventually joined Starfleet
Kahlee Sanders was a major character in four Mass Effect novels before making her in-game debut at Grissom Academy in Mass Effect 3.
Ursula, Phoebe Buffay’s twin sister (both played by Lisa Kudrow), who was a recurring character on Mad About You before making cameos on Friends
Ambessa and Mel Medarda from the Arcane: League of Legends Netflix series were later added to League of Legends as playable Champions.
Scrappy-Doo, introduced to Scooby-Doo when the show was sinking, 10 years into its run. He later appeared in several other Scooby-Doo series and films.
Morph, introduced in the pilot of X-Men: The Animated Series to be killed off permanently, was later introduced into X-Men and other Marvel comic books, and even resurrected for the revival animated series X-Men '97.
The US version of Godzilla from the 1998 movie became a part of the Japanese franchise in the 2004 movie Godzilla: Final Wars. He was given the name Zilla and was a kaiju but not THE Godzilla.
Grand Admiral Thrawn was originally introduced in a fantastic trilogy of novels by Timothy Zahn before being incorporated into Star Wars canon in The Clone Wars animated TV show. He made his live-action debut in Ahsoka after brief mention in The Mandalorian.
Ellery Queen’s secretary Nicky Porter started out on the radio show but was then incorporated in two of the novels as well as the short stories.
Five new sets of suits appeared in Power Rangers: Super Megaforce that had never been used in Power Rangers before, but had been canon in Super Sentai.