Jackie Lynn Thomas is a student at Echo Creek Academy in the Disney XD show Star vs. the Forces of Evil. She was initially Marco Diaz's crush which she is made aware in "Sleepover", and the two develop a romantic relationship from "Bon Bon the Birthday Clown" to "Sophomore Slump", in which she breaks up with him feeling they'll be miserable because Marco's trying to get over Mewni for her. In the fourth season, she gains a relationship with a Paris girl named Chloe in "Britta's Tacos".
PTE Redux Status: The jury is out. She may be included in the PTE series, but it's not entirely sure whether she will retain the mermaid genetics in SAF.
Role in the series
In SAFA lore, Jackie is revealed to have genetics of a mermaid, allowing her to breath underwater, something she wasn't aware of until she saved Star Butterfly and Marco Diaz when they saved Pony Head from trial in the unfinished ending of the SVTFOE comic 'Deep Trouble' back when she and Marco were still a couple. For New Year's Eve 2020, she decides to go to Atlantis, the home of her mermaid great grandmother, Iris Jellyfish, who was a royal mage that wanted equality between Waterfolk and humans and married a human man to make it possible. But when Atlantis gets destroyed because of many conflicts plaguing New Mewni, she decides to live in Atlantis for a while with her girlfriend Chloe to help them recover, meeting their queen, Queen Atlanta who has been waning as Atlantis' leader since the loss of her husband, and her daughter Princess Daphne (Not to be confused with the princess of Dragon's Lair), who has developed a fascination with humans and even a foot fetish, and their other friends Sir Iliad and Sir Odyssey, two rookie guards for the Atlantean Praetorian Guard, and Daphne's boyfriend Oedipus. But her biggest challenge was preventing a war against the land and sea due to the traitorous Commander Vathys, a merman who wanted Atlantis to stay in the sea and stay away from humans as one of the oldest Atlanteans who witnessed his father being killed by humans on the same day Atlantis sank into the sea, and resorting to abusing the power of the Kraken to take over the Praetorian Guard, declaring martial law, overthrowing Atlantis, and intending to melt the polar ice caps of New Mewni and flood the world. Eventually though, this was resolved. Ever since, Jackie came to adopt alot of things from atlantis, including "Dolphin Aerobics".