Marla is a formerly free-spirited girl who has grown up to be responsible yet overprotective in order to care for her brother Charlie, who has grown lonely and disconnected from her after the death of their parents. One night, Charlie sneaks out to visit a toy museum with a Playmobil exhibit. After Marla arrives and scolds Charlie for running away, a lighthouse illuminates them and transports them to the Playmobil world.
Marla and Charlie find themselves in the middle of a Viking battle, and Charlie helps them until he is kidnapped by some pirates. Frantic to find her brother, Marla goes to the nearest town hoping to ask for help, and runs into Del, the driver of a food truck whose client refuses to pay him over pink hay that causes the town's horses to sprout wings. As Marla tries to form a posse to find Charlie, Del gets her out of trouble when she shows Viking gold to the whole town, and agrees to help Marla find her brother in exchange for the gold.
Marla and Del run into Rex Dasher, a secret agent and an old friend of Del. Rex explains that a number of characters have disappeared, and the group sneaks into a villainous spy headquarters to find information about the disappearances. Despite some issues, they successfully gather the data and escape, but Rex is later captured by the pirates. He is taken away to Constantinopolis and finds Charlie, who had been locked up with other characters by Emperor Maximus, who intends to have the prisoners fight to their deaths. Rex tells Charlie that Marla had been looking for him, which encourages Charlie to break away. However, he later allows himself to be recaptured so the other characters could escape.
Del recognizes that a device used by the pirates belongs to Glinara, an alien crime lord. After meeting with her in exchange for information, Del offers to pay twice as much as he owes her. Glinara agrees and reveals that she sold the device to Maximus. However, Del is unable to uphold his end of the bargain, as Marla only had two pieces of gold left. Angered, Glinara captures them and attempts to drop them into a portal, but they are spared by Glinara's robot servant Robotitron, who hacks the portal and drops the group into a forest. Del leaves the group, upset by Marla's deception. Marla and Robotitron get lost in the forest until Marla accidentally hits a fairy godmother, who encourages her to continue her search and sends her to Constantinopolis.
Arriving at the city, Marla reaches a coliseum where Charlie is about to fight a Tyrannosaurus rex. Charlie and Marla work together to fight off the T-Rex, but to no avail. Del soon arrives with his food truck, and Marla uses the last of Del's pink hay to turn the T-Rex harmless. An enraged Maximus orders his guards to arrest them, but the guards reveal themselves to be Rex and the missing warriors, who then lock Maximus inside a cage. As everyone celebrates their victory, Marla and Charlie use the T-Rex to fly back to the lighthouse and return to the real world, where it is revealed that they were missing for only five minutes. On good terms, Marla promises to Charlie that their relationship will be mended.
In a mid-credit scene, one of the security guards finds a figure of Maximus on the floor next to a cage. As he places him on top of Mount Olympus, Maximus's laugh is heard.
- Anya Taylor-Joy as Marla
- Gabriel Bateman as Charlie
- Daniel Radcliffe as Rex Dasher
- Jim Gaffigan as Del
- Meghan Trainor as a fairy-godmother
- Adam Lambert as Emperor Maximus
To be added