At the end of "Devolution City" when Betty and Noah go out to skate, Betty is wearing her "skateboarder" clothes, rather than her normal street clothes. The last (and only other) time she has worn these clothes was in Season 1's episode "The Wizard of Orb"
Villains: Shaka Booga and Karena
Devolution City: A volcano surrounded by palm trees
Case Of The Missing Kanushu: Betty and Sparky looking around, Admiral Degill drinking a coffee and Karena looking down on them with an evil smile on her face
Admiral Degill almost dies in this episode.
The scene where Admerial Degill is on the bridge with the giant wasp is just like the scene where Gandalf faces the Balrong in "Lord of the Rings".