Thaddeus is a researcher at the Ambrette Town Fossil Lab who appeared in the episode "Coming Back into the Cold!" He's best known for his work reviving and caring for ancient Pokémon.
When Ash and his group showed up for Alexa's interview, Thaddeus gave them the full tour—fossil displays and all. The real highlight was the freezer room, a temperature-controlled habitat where the lab kept an Amaura and Aurorus they'd brought back to life. He explained that an excavation team had discovered the fossils way up north in Kalos and brought them in for revival.
Things went south pretty quickly when Team Rocket broke in and snatched the Amaura. Thaddeus rushed to help but the thieves were already gone. He stressed how urgent the situation was—Amaura can't handle heat well and wouldn't survive long outside the cold room. While Alexa and the others took Aurorus to track down the stolen Pokémon, Thaddeus prepped a transport truck just in case.
When the group successfully defeated Team Rocket and recovered Amaura, Thaddeus arrived with the truck to bring both Pokémon safely back to the lab. Once they were back in the freezer room, he confirmed that Amaura had made it through okay.
Content compiled by AnimeList.moe from publicly available sources.
