Character Rerailment: With the exception of a brief scene referencing Mr. Smoothie, Ben loses most of his silly behaviour during this episode to be a more balanced character. He also doesn't call out his aliens' names when transforming.
Fanfic Fuel: It's explicitly confirmed earlier in the special that Ben got infected with nanites upon arriving in Rex's world, and he is not shown getting rid of them at any point. The concept of Ben returning on his world with nanites inside him and as such the ability to potentially go EVO at some point leaves plenty of possibilities for fanfic writers.
Funny Moments: Rex is captured by Alpha, and the Ultimatrix is out of juice.
Rex: "Do something. Anything!"
Ben chucks a rock at Alpha, only to hit Rex's head, complete with *DONK* sound
Moment of Awesome: Several of them, but the one who gets the cake probably is Ben turning into Upgrade and fusing with Rex to fight Alpha Omega.
Moral Event Horizon: You can more or less feel sorry for Alpha's situation until he indirectly kills thousands of evo's.
Nightmare Fuel: Alpha creates his various bodies by absorbing nanites from other Evos, similar to Van Kleiss in the first season. Except instead of being turned to stone, they are reduced to ashes. Now remember that Alpha did this to various Evos over the special, and some of them might have been humans...
Go to extreme when he goes to the Bug Jar and absorbs almost every Evo in it.
They Wasted a Perfectly Good Character: Despite how useful the transformation would have been (not to mention being given ample opportunity to use it). Ben never transforms into Way Big once during the movie.