When Max pulls down the screen showing the locations of all the plumbers' bases, it doesn't show any of them being in South Dakota, despite it being the location of Mt. Rushmore.
Look Hard: When the Omnitrix gives it's warning beep, the red beeping isn't seen but heard.
Look Closely: When Rojo cuts the main cable, Diamond Head's eyes are green and round, similar to Tetrax's.
Pay Attention: When Cooper mentions his grandfather telling him about the spellbook, he is pointing at Ben; the same goes for the Omnitrix and Gwen.
Pay Attention: Ben remains as Diamond Head, it seems, a lot longer than 10 minutes in this episode.
Cooper said that his grandfather told him about the Omnitrix and Gwen's spellbook. But what would Gwen's spellbook have anything to do with aliens or the Plumbers?
Think Back: Gwen and Max refer to the Forever King, Clancy and Rojo by name, despite never learning their names in their debut episodes. They also did this with Hex in "Tough Luck," Enoch and the Forever Knights in "Ultimate Weapon", Tetrax in Ben 10: Secret of the Omnitrix, and Cash and JT in "The Unnaturals".
Diamond Head: (after stopping the Rust Bucket) See? No problem.
Gwen: (observing the damage) Tell that to the road crews!
Grandpa Max: The circus freaks couldn't figure out how to steal water from an aquarium!
Gwen: That's Clancy!
Diamond Head: The bug guy? I thought he was gone for good!
XLR8: Okay, let me get this straight. The circus freaks break into the biggest bank in the world, but forget to steal any of the gold?
Joey/Rojo: You're still alive? You're making me look bad.
Cooper: In other words I'm pretty good with computers and stuff like that.
Gwen: (presenting to Cooper her laptop) Then you'll love this. It's the new XT900 with satellite uphook. Use it whenever you like.
Ben: (slamming down the laptop) Not fair, that's bribery!
Gwen: (pulling out one whole bucket of stuff) Oh, and what do you call this?
Ben: Gwen, I'm not selfish as you are, some of us enjoy sharing.
Gwen: I'm telling Grandpa!
Ben: About what? You're a big doofus?
Grandpa Max: Ben, get up here.
Gwen: Ooo, busted!
Grandpa Max: You too, Gwen.
Grandpa Max: Hi guys, this is Cooper, the grandson of an old Plumber buddy of mine, and...
(Gwen and Ben were fighting over the handphone)
Gwen: Doofus! Give me it! You're wasting time!
Ben: I heard it first, I get to call!
Forever King: Behold, the Negative 10!
Ben: Oh, man. (sounds scared)
Gwen: Charmcaster? Is there anyone in on this who DOESN'T hate us?
XLR8: I don't want to hurt you guys. (the hypnotized guards shoot at him) Guess the feeling's not mutual.
Cooper: (about the Hypnotized Guards) Why'd they shoot at us? We're the good guys!
Gwen: Yeah, we get that a lot.
Grandpa Max: Maybe Cooper should stay here.
Ben: Don't worry, Grandpa, I'll look after him. He probably wants to see the Omnitrix in action anyway.
Stinkfly: Now you see me, now you don't.
Running Gag: Rojo and Charmcaster arguing to see who's more special.
Sublimino has no dialogue in both parts of the episodes.
Final appearance of every enemy in the show except Vilgax and Dr. Animo.
Final appearance of Stinkfly.
This episode airs in the US with both part one and two in a special one hour premiere.
This episode is kind of in reference to the Ben 10 game Ben 10: Protector of Earth, where in the game, Ben faces every (almost every) enemy he has.
Animo calls Ben by his full name (Benjamin) for the first time.
It seems this episode happened before "Goodbye and Good Riddance", seen as it is still summer, and Ben is still traveling with Max and Gwen.
The Forever King's Negative 10 consists of himself, a ninja from the Forever Knights, Sublimino, Clancy (now mutated into an insect-like form), Rojo (in a new armor), Charmcaster, Dr. Animo, and the Circus Freaks (Thumbskull, Frightwig, and Acid Breath).
Alien Form(s) Used:
3) Diamond Head
Charmcaster appears in this episode without Hex, who she is supposed to be babysitting.
Second appearances of the Forever King ("Perfect Day"), Sublimino ("Midnight Madness"), Clancy ("Side Effects"), and Rojo ("The Alliance"). Sixth (seventh if you count "Goodbye and Good Riddance") appearance of Animo ("Washington B.C.", "Dr. Animo and the Mutant Ray", "Ben 10,000", Ben 10: Secret of the Omnitrix, and "Divided We Stand"), fourth appearance of Charmcaster ("Tough Luck", "A Change of Face", and "Don't Drink the Water"), and third appearance of the Circus Freaks ("Last Laugh" and "Ghostfreaked Out").
The camp Cooper gets picked up from appears to be Camp Opinicon from "Camp Fear."
The Negative 10
The Forever King's plan to unite a handful of villains to get what he wants, is similar to the main plot line of the fifth season of Teen Titans.
The Forever King: I find your lack of faith disturbing.
Reference to Darth Vader's line in A New Hope.