Undercover

Undercover is the eighteenth episode of Ben 10: Alien Force.

Airdate
November 14, 2008

Plot
Kevin, Gwen, and Ben destroy a teleporter they were working on and need help repairing it. Kevin suggests Cooper, the young boy who had helped the Tennysons in the past. Unfortunately, Cooper has been kidnapped by the DNAliens. They track him to the abandoned military base where Paradox built his time machine. They discover that the Highbreed have erected a cloaking field, built by Cooper over the area, concealing a mysterious arch-like device. They free Cooper and have him destroy the cloaking generator, during which he has visions of the arch acting as a gateway for a fleet of ships and the Earth being destroyed. Despite destroying the generator, the Highbreed manage to repair it and continue their operations unhindered.

Major Events

 * The DNAliens kidnapped Cooper for their plans.
 * Ben and the gang retrieves Cooper.

Characters

 * Ben
 * Gwen
 * Kevin
 * Cooper (first appearance since the original series)

Villains

 * DNAliens
 * Highbreed Commander

Aliens used

 * Swampfire
 * Goop
 * Echo Echo

Trivia

 * When Kevin told Ben that "he used to turn into insect", he was referring to Stinkfly.
 * Though Kevin shows tendencies of being protective, jealous and mad when other guys had a crush on Gwen, but he was surprisingly good humoured towards Cooper for his adolescent feelings for Gwen.
 * The second hint towards the events of War of the Worlds are foreshadowed when Cooper was destroying the machine.
 * DNAliens cannot handle very high frequency sounds.
 * Kevin knows Cooper for unknown reasons (probably dealing with alien-weapons and advanced technology).
 * Cooper from the original Ben 10 series makes a return appearance. Apparently, he has gained a lot of weight in the last 5 years since he spent too much time in his lab.
 * When Cooper is talking about Princess Elena in Nations of Conquest, it can be a possible but untrue reference to Elena Validus in Alien Swarm.