When their planet's monarchy is overthrown by a coop, royal alien teens Aja and Krel fleed to Earth accompanied by their brutish bodyguard.
- Tatiana Maslany as Princess Aja & Queen Coranda
- Diego Luna as Prince Krel
- Nick Offerman as Commander Varvatos Vex
- Glenn Close as Mothership
- Cole Sand as Eli Pepperjack
- Andy Garcia as King Fialkov
- Hayley Atwell as Zadra
- Alon Aboutboul as General Morando
- Jennifer Hale as Izita
- Chris Obi as Loth Saborian
- Goof: The episode shows the ship crash-land in Arcadia at dawn, whereas in the Trollhunters episode "A Night Patroll", the ship is seen landing at night.
- Eli's voice becomes much deeper, starting with this episode (understandable, as his voice actor, Cole Sand, has further matured since starring in Trollhunters).
- This is lampshaded by Eli himself, as well as Steve Palchuk in the later episode "Party Crashers" when Eli implores Steve to "Listen to [Eli's] voice, Steve. I've matured. And mature people go into the woods and hunt the legendary Arcadian Billycraggle." Steve rebukes with "Shut your manly voice!" so that Eli doesn't blow their cover as Creepslayerz.
The image gallery for Terra Incognita Part One may be viewed here.