When asked on Twitter about if she will return to play Holiday in the crossover, Grey DeLisle said "I hope so".So apparently at the 2019 new York toy fair they released a special first look of the toys for the season 4 of the ben 10 reboot, and I was pretty surprised as what I saw.
Six is voiced by Vic Chao, replacing Wally Kurth from the original Generator Rex series, due to the producers being unable to contact Kurth.This is also the fourth crossover with Generator Rex in general if the comic Hero Times Two and Rex's cameo in Crossover Nexus are counted.As such, Daryl Sabara and John DiMaggio both reprise their roles as Rex and Bobo from the original Generator Rex series. This is the second movie/special to crossover with Generator Rex, the first being "Ben 10-Generator Rex: Heroes United".Duncan also confirmed Vic Chao would be be making a guest appearance, but avoiding spoiling which character Chao would be voicing.A crossover between the Ben 10 reboot and Generator Rex was first hinted by Duncan Rouleau, though it was intended to air during season 3 before being postponed for season 5.This special is the crew's way of rectifying the scrapped "shared universe" concept.
However, the idea never came to pass back then due to both series having different toy licenses.
Heatblast burns the flute turning the living trees into normal trees, and makes hex mad as usual. Gwen tells Heatblast to go for the flute and shoots a fire at him, causing him to drop the flute. Hex makes more living trees and begins to overpower Heatblast. The family returns wanting to thank Heatblast for getting rid of the living tree, but Heatblast tells them to run. Hex appears and uses the powers of Pans flute to make more living trees. Heatblast burns the tree, almost causing a forest fire, until Gwen and Grandpa Max put a blanket for the burned tree. The episode begins with Heatblast battling a living tree near a family roasting marshmallows. When Ben meets a young Rex Salazar on the run from a hostile Providence, he must work through a series of misunderstandings, and defeat the dark wizard Hex in order to save the world from a malfunctioning Omnitrix infecting the world's human population with alien DNA.