This is the first episode of The Tennyson Trio.
Plot:
This episode starts out exactly the same as the beginning of the first episode of Ben 10, so I'll skip to when Ben is about to go on a walk and get the Omnitrix.
Ben: This is boring. I'm going on a walk.
Ben sees the shooting star.
Ben: Cool, a shooting star!
It goes towards Ben.
Gwen: Look Grandpa, a shooting star!
Max: Wait! I think it's heading to Ben's location!
Gwen and Grandpa Max run to where Ben is, and now the pod has landed.
Max: Ben! Are you okay?
Ben: Yes.
The pod opens up, revealing the Ultimatrix and the Omnitrises from Original Series and Alien Force.
Gwen: Wait! What are you doing?
The Ultimatrix jumps onto Ben's wrist. Max and Gwen try to help Ben get it off, but the Original Series Omnitrix came on Gwen's wrist, and the Alien Force Omnitrix came on Max's wrist.
Ben: Get it off, get it off!
The Ultimatrix core shows a hologram of NRG, and Ben slams it down. Ben screams.
Max: Don't freak out.
Ben accidentally shoots fire from his eyes and causes a forest fire.
Gwen: Ben!
Ben: Sorry, it's not my fault!
Max: Maybe if we can figure this out, we can put the fire out.
Grandpa Max pushes the button on the Omnitrix and transforms into Big Chill. Max freezes the fire. Ben and Max touch the Omnitrix/Ultimatrix symbols and change back.