|Original broadcast||October 6, 2007|
|Written by||Greg Weisman|
|Directed by||Sebastian Montes|
|Previous episode||Ready to Rumble|
|Next episode||Ben 10 vs. the Negative 10: Part 1|
Ken 10 is the forty-sixth episode of Ben 10.
Ben 10,000 is fighting Vulkanus and sends him into the Null Void. He then gets home just in time for Ken's birthday party. The relatives come and give him gifts; Gwendolyn gives him a rock pet, Max gives him a hoverboard and he receives an Omnitrix from Ben.
When Ben leaves to go fight more crime, Ken turns into XLR8 and races with him. While fighting, people and aliens watch the fight (also a kid that looks like Kevin while they were fighting Mot Snikrep).
Ken finds out that Ben put a limiter on the Omnitrix to keep Ken from heroing on his own and is displeased because Ben won't let him fight. So he becomes friends with Devlin after playing on his hoverboard. Gwendolyn talks to Ben about kids and their ways making Ben decide that the next time there's an attack, they'll fight together.
At night, someone tries to attack Ben and Ken. Ben finds the intruder is Kevin. Ben tells Ken to go to his room because he's too strong, unwilling to let Ken fight despite the promise he made.
The next day, Ken tries to find the Null Void on his own with Devlin hoping to impress his father by finding out how Kevin escaped the Void. Turning into Ditto, Ken finds the Null Void chamber and much to his horror discovers that Devlin is the son of Kevin, who had attacked the house last night in search of the chamber using Kevin's original mutant form. Devlin releases his father just in time for Ben to arrive. Kevin reveals that being imprisoned in the void was the best thing that ever happened to him as he has now absorbed that powers of 11 000 aliens and transforms into a even more monstrous form than before. Kevin mercilessly attacks Ben, Ken and even his own son Devlin. While Ben takes the fight outside Ken has a idea to defeat Kevin.
Ben still fights Kevin, but as before weakens Ben, making him revert back to human form. Ken comes in as Grey Matter and later switches to Spitter, then Buzzshock. Ken reveals he used Grey Matter's brain to remove the Omnitrix's limiter so he can switch forms at will. Kevin grabs Ken and is about to throw him, but Devlin comes in to defend him. Devlin explains why he freed Kevin - he wished his father would have cared about seeing his son again but instead finds that he doesn't care at all as he is only willing to kill the Tennysons. Devlin cries upon this realization but then resumes fighting against his father. Ken turns into XLR8. Devlin and XLR8 are thrown away and XLR8 reverts back into Ken who passes out.
Ben wakes up and sees what happened to Ken, angering him. He turns into Way Big to mercilessly crush Kevin, who reverts back into human form, but is still strong. Kevin is about to kill Ben and Ken, but Devlin imprisons Kevin in a Null Void Grenade. Max states that he has a 'special place' reserved for Kevin so he can't absorb any more alien DNA. Ken asks Ben if he can use all ten thousand of his heroes, but Ben says not to push his luck.
Devlin is about to leave until Max grabs him. Ken says he should stay with them, so Devlin becomes part of the Tennyson family. Later, Ken's rock pet regenerates and is alive again making him happy.
- Ken receives his own Omnitrix.
- Ken meets Devlin.
- Kevin escapes from the Null Void.
- Devlin moves in with the Tennysons.
- Ken Tennyson (first appearance)
- Ben 10,000
- Gwendolyn Tennyson
- Max Tennyson
- Gwendolyn Tennyson (Ken's sister; first appearance)
- Devlin Levin (first appearance)
- Ken's Pet (first appearance)
- Billy (first appearance)
- Alien Kid
By Ben 10,000
- Four Arms (x4)
- XLR8 (x4)
- Cannonbolt (x2)
- Diamondhead (x2)
- Way Big
- Though the party is for Ken's 10th birthday, his cake is erroneously depicted with 11 candles. However this can be chalked up to some people putting an additional candle on a birthday cake for good luck.
- When Ben arrives for the party as XLR8, there is nothing behind him but when he reverts there is a 'Happy Birthday' poster and other decorations behind him.
- When Four Arms throws Devlin, his back is drawn incorrectly.
- When Ken falls into his room, rock pet loses a stripe on the back.
- When Kevin is seen on top of the Null Void containment unit, he had white lines as a design on his shoes. After that, his shoes are completely black.
- When Kevin 11,000 is in his mutant form, sometimes his toes are red, other times they're the color of his tentacles.
- Kevin 11,000 normally has four Null Guardian tentacles, but in one scene he has seven.
- Although Ken has unlocked the Master Control, the Omnitrix timed out.
Naming and Translations
|Hungarian||Ken 10||Ken 10|
|Portuguese (Br)||Ken 10||Ken 10|
|Spanish (HA)||Ken 10||Ken 10|
|Spanish (Spain)||Ken Ten||Ken Ten|
- One of Ken's friends who attends his birthday party bears a close resemblance to Billy from The Grim Adventures of Billy & Mandy. He also shares Billy's voice actor, Richard Horvitz.
- This episode celebrates the three year anniversary of the series.
- It is revealed that adult Gwen can tame rock monsters as pets.