Jayna and her brother Zan are aliens from the planet called Exxor. They were different than other Exorians and classified as mutants due to genetic throwbacks. Supposedly there once existed an ancient race of Exorian shape-shifters. Their parents died when they were still babies (during a plague), and, because of their origin, no Exorians wanted to adopt them. They ended up adopted by the owner of a Space Circus, who only wanted to use them as sideshow attraction. Fortunately, the circus's clown was a kind man and raised them. He also gave them Gleek as a pet. Eventually, as teens, the pair escaped the circus and hid on a planet where a space villain called Grax (an enemy of Superman) had set his headquarters. Spying on him, they learned that Grax was planning to destroy the Earth using hidden explosives. The twins decided to travel to Earth and warn the Justice League (this was how they came to replace Wendy and Marvin who were planning on retiring as heroes anyway supposedly) as their sidekicks.
Jayna was created by E. Nelson Bridwell and Ramona Fradon
The heroes also arranged for the kids to live with an old scientist called Professor Cartel Nichols, and they even took secret identities as John and Joanna Fleming and used the idea they were transfer students from Esko, Sweden . They disguised themselves with blond hair (Jayna used her powers to transform into a human to change her hair color and ear shape), to allow them to attend Gotham City High School.
Modern Age: New Earth
During the late 90s the twins were introduced into the main DC Universe in the series called Extreme Justice . Their origins were retconned from being sideshow attractions to slaves of an alien villain, later rescued by the Justice League. They appeared they were much more powerful than their previous cartoon incarnations and they were unable to speak English.
Major Story Arcs
Modern Age: New Earth
In issue 9 of Extreme Justice, they accidentally attack some civilians and the Justice League. They later join Captain Atom 's team. Later they are seen with Young Justice in invading the country of Zandia in order for Empress to get revenge on her parent's killers.
Powers and Abilities
When Jayna touches her brother she can assume the form of any animal, even mythical ones such as a werewolf, a griffin, and a sea serpent. She also shares a telepathic link with Zan.
Jayna and her brother only appeared in the television show Super Friends and comics based on show and never appeared in the DC Universe at that time.
Justice League Unlimited (Cartoon Series)
A version of the Wonder Twins appeared in a episode of Justice League Unlimited with a group of man made meta humans named the Ultimen. Jayna was renamed to Shifter and appeared as a white skin meta human girl. She was also able to turn into animals with making contact with her brother. The appeard in episode 9 of the series titled Ultimatum. They were created by S.T.A.R. Labs in hopes of making a team that is controlled of heroes instead of the Justice League. Each on of them had a false history and were believed they were normal meta humans.
Teen Titans Go!
Jayna, with her Wonder Twin, appears in the show.
Lego Batman Movie
The Wonder Twins are among the heroes present in the Justice League anniversary party , to which Batman has not been invited.
Smallville (TV Series)
The past of Jayna and her twin brother Zan is unknown. Both always told that they were transfer students from Sweden but no one believed that. Since that, Zan and Jayna were living on the streets their entire lives. The only other history they have was that they once had a father who told them to always stay together, because the are stronger as a team. The origin of their powers are also unknown. Zan and Jayna are proud fans of The Blur (later known as Superman) and tried to follow in his footsteps.
Jayna was played by the actress Allison Scagliotti who also played the character Claudia Donovan on the TV series Warehouse 13. Both, Zan and Jayna only appeared in one episode of season nine, called "Idol".