And Then What?: At the end of the Umbara arc, a dejected Rex and Fives discuss the war. When Fives attempts to cheer Rex up by pointing out that the war will eventually end, Rex wonders what will happen to all the clones once it does. Fives does not know, and cannot think of anyone who does.
Bad Guys Do the Dirty Work: Once Captain Rex captured General Krell, he was going to execute him to prevent him from being freed by the Separatists. Dogma ultimately pulled the trigger for him.
Bittersweet Ending: Krell is killed for betraying the Republic by Dogma (who still goes to jail for being supportive of Krell earlier), and the Republic has secured Umbara. They did it! Woohoo! Rex however is not in the mood for celebration, because one, so many 501st clones were killed taking Umbara, and two, Rex is now left wondering about the point of the Clone War.
Call Forward: When Captain Rex leads a squad to attempt to arrest Krell, the entire sequence and the nature of their actions are strongly reminiscent of both Order 66 and Mace Windu's attempt to arrest Palpatine. Krell even says "It's treason, then" before tearing into his would-be captors, just as Palpatine did before tearing into his would-be captors.
Colour-Coded for Your Convenience: Played straight and subverted. The Clone Troopers are members of the 501st and thus wear blue, and the "enemy Umbarans" wearing stolen uniforms wear yellow. Except the "enemies" are actual clone troopers from the 212th Attack Battalion, and both sides have been told the other were impersonators so they would wipe each other out.
Continuity Nod: In the episode, Dogma is warned to avoid stepping on one of the vines lying on the ground, with Tup pointing out that it is actually a tentacle for a vicious carnivorous creature and that he saw Hardcase attacked by one just like it. That happened in the first episode of arc, "Darkness on Umbara."
Dual Wielding: General Krell dual-wields double-bladed lightsabers!
Dies Wide Open: The 212th Attack Battalion Clone that Rex unhelmets and finds out that his troops are shooting at other Clones.
Evil Laugh: Once General Krell admits that he is a traitor, he laughs deeply in every following conversation.
For the Evulz: Once General Krell admits that he was a traitor, Captain Rex asks him why. "Because I can. Because you fell for it. Because you're inferior."
General Failure: Pong Krell. It is better to have rested soldiers than tired soldiers, better to have high morale than low morale, and better to attack from cover than to attack without any cover. Krell sent tired soldiers to attack a city out in the open where they could be easily gunned down like fish in a barrel, and all this after letting them all know that as far as he was concerned they were expendable pieces of junk. He's no Sun Tzu, that's for sure. As it turns out, he's intentionally sabotaging the Republic's efforts on Umbara so he'll have a good accomplishment to present to Dooku when he defects to the Separatists.
Heroic BSOD: Rex has a brief one after finding out about the fact that his troops were killing other troopers after being tricked by General Krell into thinking that they were Umbarans.
Informed Ability: Much talk is made about how General Pong Krell's tactics are very effective, but every command he issues during the show leads to defeat that his troops need to reverse by disobeying his orders. Even the opening narrations of the previous episodes describes him as reckless. It turns out he was deliberately sabotaging the Republic advance prior to his planned defection to the Separatists.
My God, What Have I Done??: Though Rex doesn't say this, the look on his face after he founds out about the fact that his troops shot his own comrades spells this.
Tup however says this without the "my god" ("This can't be happening. What have we done?").
Silly Rabbit, Idealism Is for Kids!: General Krell claims that is no longer naive enough to believe in the ways of the Jedi, which is why he is planning to betray the Republic and defect to the Separatists.
They Call Me Mister Tibbs: When Rex finally decides that General Krell is going too far in his treament of Clone troopers, he affirms that he is to be addressed as "Captain," not CT-7567.
Tyrant Takes the Helm: The Umbara arc opens with Anakin being recalled to Coruscant and General Krell being given command of his clones. He immediately begins to denigrate the troopers, insulting their laboratory origin and, and giving them horrible tactical orders. Turns out that was all intentional: he is planning to defect to the Separatists and wants to degrade the exclusively referring to them by their identification numbers Republic war effort before he does as a gift to Dooku.
The Uriah Gambit: General Krell's horrendous battle tactics were revealed to be part of his plan to sabotage the Republic advance in preparation for his defection to the Separatists. By giving his troops impossible assignments they would be easily defeated, and ultimately wiped out, by the Separatist forces.
Wham Line" A dying Waxer delivers one, revealing that General Krell set two battalions of clones against each other, planning for them to all be killed.
Rex: Tell me who gave you orders to attack us.
Waxer: It... it was General Krell. He sent us to these coordinates to stop the enemy. We thought they were wearing our armor. But... it was... you...
You Fool!!: At the conclusion of Umbara arc, General Krell decrees that Dogma was "the biggest fool of all."
What Could Have Been: Originally, Rex was going to be the one to pull the trigger and kill General Krell, but ultimately, it didn't fit his character, so they had Dogma do it instead.
Who Dares?: Pong Krell when Rex and the clones attack him.
You dare to attack a Jedi?!
You Wouldn't Shoot Me: When Captain Rex is going to execute General Krell, Krell taunts him over his inability to pull the trigger and his inherent weakness. Too bad for him that Dogma is there to pull the trigger.