Spy Kids 2: The Island of Lost Dreams
Gerti is first seen in the second film of the Spy Kids series, at Dinky Winks' theme park with her older brother Gary Giggles coming to supposedly help with Juni Cortez and Carmen Cortez rescue the president's daughter Alexandra.
While Gary and Juni get in a fight on a device called The transmooker, Gerti has ponytails that spin allowing her to fly, kicking one of the evil henchman waiters (who are actually Magnamen) in the head.
At the end of the fight the transmooker device gets caught by a different evil waiter, who is secretly working for the sinister side of the OSS. Gary blames Juni for the theft of the transmooker, and gets him fired from the OSS.
Later in the movie Gary and Gerti get assigned to a Level 1 mission (Juni and Carmen spy on them with a camera planted in Juni's "pet" robot bug, R.A.L.P.H.). Carmen Cortez gets them put on the same mission as Gary and Gerti (Juni reassigns their destination to Gobi Desert) and levels herself from Level 2 to Level 1 and reassigns Juni to the OSS.
Carmen and Juni make it to the island first. On the island Carmen and Juni take an efficient route to the Transmooker device while Gary and Gerti take the same way at a slower pace. While on the way, Gary and Gerti get in to trouble with a slizzard, forcing Carmen and Juni to help them. Later, the girls happen to get snatched by a giant pig named Sporky that can fly (made by the island's hermit named Romero).
While the girls are caught with Sporky, the boys, Juni and Gary, have a fight with two hybrid animals that they have happened to befriend. Carmen convinces Gerti to turn on Donnagon Giggles, her father. At first, it seems like she is helping her father. But when Donnagon fires up the bigger transmooker, it destroys its core. When questioned why she turned on him, Gerti simply threatens to tell her mother, who is unaware of Donnagon's evil misdoings, that Donnagon tried to conquer the world again. Then, she promises Carmen to straighten Gary out if he gets out of line, because Carmen has had a crush on Gary, and the two bump knuckles with a smack.
Spy Kids 3-D: Game Over
In the third Spy Kids film, Spy Kids 3-D: Game Over, Gerti flies by at Juni's clubhouse, wondering when he will rejoin the OSS. Before leaving, she reminds him that "everyone's your family". Later, she is called for assistance in fighting off the evil Toymaker's robots. After the battle, all the Cortezs' allies, including Gerti, join into one family union. At the end Gerti and Juni wink at each other.