When Graham launches to take on Johan Billy chides him for being reckless and his response? "Sounds reasonable! Too bad I'm an unreasonable man!"
In season one, when Louise finally manages to get her mother to accept Saji (by showing her his status as a nigh-Woobie that needs to work more than one job to help his sister pay their rent) she suddenly says she sees her husband in him. Louise is NOT pleased.
Louise: No! Dad's still alive!
Later on, while watching coverage of another event involving Celestial Being, astounded Louise's mother holds onto Saji's arm as they watch.
Louise: Let go of him!
Anytime Patrick Colasour Epic Fails at combat, and somehow lives through it anyway. "Not AGAIN!"
What's especially hilarious is that he gains a reputation as "The Immortal Colasour" ("Colasour the Indestructible" in the dub) for surviving so many battles with the Gundams.
Changes it to "Colasour the Ridiculously Lucky" after getting married to his superior officer at the end of Season 2.
Orange Haro: I wanted to see you! I wanted to see you! Big brother! Big brother! Purple Haro: Who the hell are you? Who the hell are you? Orange Haro: Haro! Haro! Purple Haro: Don't know ya! Don't know ya! [Bumps Orange Haro...] Orange Haro: (Fading away from the scene) Big brother, your memories! Big brother, your memories! Big brother, your memories!
Made better because he mentions it was Sumeragi's idea. One wonders how long she'd wanted to do that...
Season 2 Episode 18. A battle is going to start, and everyone says the name of a person he/she love most, either a romantic interest, or a family member... except for Tieria and Setsuna, who said "Veda" and "Gundam", respectively.
Ribbons Almark finding 0 Gundam and calling it in excitement his dream all along. This might not be as obvious as the examples above, but think about it! This has been done intentionally given that Ribbons Almark shares the same voice actor with Amuro Ray! Wouldn't it be funny to imagine Amuro wetting his eyes for finding the RX-78-2 once again so many years after losing it??
Even Ali al-Saachez is capable of these. When Nena meets him in the second season, she angrily recognizes him as the man who killed her brothers. His response? A cheerful "Get out! I knew you looked familiar!", as though greeting an old aquaintance.
Everyone meeting Ian's wife Linda... and remarking on their age difference.
Saji: "Wow, she's young."
Allelujah: *smirking* "There oughtta be a law."
Ian: "Shut up!"
Lyle finding Allelujah and Marie making out in Season 2 episode 7.
Haro: Allelujah detected! Allelujah detected!
Lyle: *sees Allelujah kissing Marie* What the hell? All this trouble to find him, and he's been hanging out with some girl! Way to go, pal!
Lyle confessing to Anew and the others' reaction to it.
Mileina: AMAZING! The flowers of Love have finally blossomed!
Gundam 00: A Wakening of the Trailblazer has Patrick repeatedly failing to call Kati anything other than "Colonel" ("How many times do I have to tell you it's Brigadier General!"), Mena Carmine and her hyperactive crush on Billy, and Mileina confessing her love to Tieria ("No matter what form you take!"), eliciting a "WHAT THE HELL!" from her father.
Early in the movie, Hallelujah uses mad Le Parkour skills to escape from ELS-controlled vehicles, winding up on top of a building looking down at the cars. He shouts "You can't get me up here!" The ELS respond with a helicopter.
Not to mention the in-universemovie depicting the battle between A-LAWS and Celestial Being... as an unashamed Super Robot show complete with Scenery Chewing galore, multicolored Trans-Am effects, Lockon as a pink-haired Meganekko, Tieria as a Scary Black Man, and an Ahead using the Tengen Toppa Gurren Lagann glasses-boomerang attack. Then cut to Saji, who's looking all unimpressed, remarking how real combat is nothing like that, and lamenting that he wasn't in the movie at all.
The fansub group [gg] had loads of fun with this scene, basically using it as a vehicle for mocking bad Fan Sub practices such as extravagant fonts, leaving words untranslated, and putting "Translator's Notes" all over the place.
Mission 2306, Another Story. Dear God, just... Another Story.
Haleluiah becoming a school bully (After Setsuna and Tierria had hypnotized him into doing so) and assaulting Saji, only to get completely curb-stomped by Graham, who was calling his attacks!