What makes this scene even funnier is that: 1. Sari, an 8-year old human child, gives The Talk to Optimus Prime, a billion years old robot, and 2. the implication that somehow Sari possesses enough understanding of concepts of human sex and birth to pass to someone else.
On a meta-level, it's funny that they killed Optimus off in the first episode and revived him within 75 seconds. All while homaging his death from The Transformers: The Movie. You can just imagine someone in the writer's room thinking "Alright, Optimus death and inevitable revival is out of the way. Moving on."
"Thrill of the Hunt" opens with Ratchet and Optimus Prime checking out second-hand auto parts dealer shop. Ratchet displays his disgust at selling mechanical parts (they are living robots after all), while Optimus doesn't seem to mind as he understands that this must be some sort of human custom.
Ratchet: It's primitive...it's barbaric...there ought to be a law against it!
Optimus Prime: ...It's just an auto parts supply store, Ratchet.
Ratchet: You mean they actually sell spare parts on the open market? What kind of malfunction would be crass enough to buy this stuff?
Don't forget Lugnut's unique devotion. It even annoys Megatron himself:
Lugnut: I WILL NOT HIDE! I WILL STAND PROUDLY AND SHOUT MEGATRON'S NAME TO THE HEAVENS!
Megatron:Oh, for spark's sake... Lugnut, you iron brained idiot. We don't need to attract any unnecessary attention...
Nature Calls: Let's not forget what happens after Bumblebee tries to use his media player in conjunction with Prowl's hologram projecter to watch a horror movie... and when Prowl crushes Bumblebee's media player...
From "Megatron Rising Pt. 1", Starscream is in the middle of monologuing to Megatron about how easy it would be to walk right in and terminate him in the state hes in. Then Bumblebee charges in directly firing at Starscream. Starscream doesnt even flinch and is more bothered by something else.
Lugnut: Oh, Master! I am not worthy, I am not worthy... (Beat) What happened to your body? Megatron:Long story. Blitzwing: (in Icy mode) So you didn't have voices in your head... (switches to Random mode) YOU HAD A HEAD IN YOUR HEAD! A-hahahaha!
From "The Elite Guard". "Ohhh, I get it. You're afraid of me, aren't you? BOOGABOOGABOOGA!" "AHH!" The best part is probably Jazz's terrified pose.
"I will pound you into sheet metal!" *faceswap* "Wait, we've already got some!"
Sentinel [as Optimus fights the Headmaster, who has stolen Sentinel's body]: You're enjoying this, aren't you, Optimus?
Optimus: [smirks while continuing to pound the Headmaster, which Sentinel can feel]
In the Allspark Almanac databook, a self-serving diary entry from Sentinel Prime makes this even better. "Let me say that again. Optimus. Ripped. My. Arm. Off."
From earlier in that episode, Optimus's reaction to seeing Sentinel Prime as just a head is gold. Hearing Optimus Prime of all bots laugh is just a great moment.
Sentinel: Uhhh, Optimus. Tell the organic Fanzone that he can send his police force home. It's a false alarm. Optimus: How do you know? Sentinel:I just know, okay?! Now I need you to come to my position. ALONE. And promise me one more thing... Optimus: What? Sentinel: That you won't laugh! [cut to Optimus looks around the rubble for Sentinel] Optimus: Sentinel? Where are you? Sentinel: (quietly) Look down... [Optimus looks down to see Sentinel's head severed from his body, a comedic cue plays as the camera pans down to the body-less Sentinel, and Optimus cracks up at the sight] Sentinel: You promised you wouldn't laugh!
Also, "You kicked me! On purpose!"
Sentinel gets a bit snippy, and Optimus can return in kind, even while fighting.
Sentinel Prime: Hurry it up, Optimus Prime! That boat, and my body, are getting away!
Optimus Prime: Would you prefer for me to use you as a shield?! Actually, that's not a bad idea.
Sentinel Prime: Now, now, Optimus, let's not lose our I-I mean youknowwhatImean.
In general, Sentinel attracts situations like this. His whole visit to Earth consists of him being haughty and then having bad things happen to him. Case in point, his first time out driving, he disrespects human traffic laws and discovers that they're there for a reason when he drives off an unfinished overpass, after having blown through the clear signs warning drivers not to go that way.
In fact, how about we soak up the Irony of how Starscream attacks Megatron while Megatron is giving a speech about how the Decepticons must unite in order to defeat the Autobots and regain control of Cybertron?
Megatron giving Lugnut orders in "Garbage In, Garbage Out". Seeing how this is Lugnut....
Lugnut: STASIS LOCK ITSELF COULD NOT DETER ME FROM YOUR GRAND, AND GLORIOUS PLAN, OH WISE AND NOBLE MEGATRON! Megatron:Just...go....
And earlier, Sari trying to teach Ratchet some manners:
Ratchet: Will you get in already!? Sari: Ah, ah, ah, what's the magic word? Ratchet:NOW!
After Lugnut's failed Punch of Kill Everything:
Lugnut: Raargh! Those accursed Autobots will pay for their insolence! Wreck-Gar: Right! [pulls out a smoking cash register] Cash, check or charbroil? [Lugnut smacks the cash register aside.] Lugnut:ATTACK! Wreck-Gar: Right! What kind of tack would you like? Thumb tack? Carpet tack? Income tack? Lugnut: Argh, never mind
During the final confrontation with Wreck-Gar:
Ratchet: You glitch-head! You're gonna destroy the whole city! You wouldn't dare do something that stupid! Wreck-Gar: I am Wreck-Gar! I dare to be stupid! I will destroy the whole city! Ratchet: All right, you've forced me to make the ultimate sacrifice; to do the one thing that requires more courage than anything I've ever had to do in my entire Autobot career! I... apologize. Wreck-Gar: Come again?
Heck, pretty much everything said or done by Wreck-Gar in the episode counts!
After Ratchet saves Bumblebee.
Prowl: I'll stay with Bumblebee. Ratchet: Try to keep him quiet. Prowl: You do realize this is Bumblebee. Ratchet: Oh, yeah.
At the end of the Season 2 finale, Megatron in stasis cuffs and Starscream's detached head are stuck somewhere in space, unable to do anything but bicker:
Megatron: Stop staring at me.
Starscream: No. You stop staring at me!
Megatron: Do you think I actually want to spend the rest of eternity gazing at your unsightly visage?
Starscream: Trust me: your visage is no picnic either. And your face is ugly too!
Megatron: Oh, someone just take me offline now...
Starscream: What do you think I've been trying to do for the last four million stellar cycles?!?! AHHAHAHAHAHAHAHAHA! It's funny, really, when you think about it. Tragic, but funny! AHAHAHAHAHA!
Megatron: ...oh, shut up.
Megatron and Starscream's battle of wills continues in the Season 3 premiere "TransWarped", where Starscream gets so fed up that he starts ranting about how Megatron got them into this mess: "Are you seeing a pattern here? THIS! IS! ALL! YOUR! FAUUUULLLLTTTTT!"
Bulkhead explaining the situation of "Where Is Thy Sting?" in the most Bulkhead way possible.
Bulkhead: Oh, it's okay, he's Bumblebee, I know cause I pushed a wall on Sentinel and he told me!
All of Blitzwing in "Human Error". Even a horrible injury wont faze him for long.
Blitzwing: "Oh, look! I have a hole in my rocket!"
Human!Prowl: It's merely a matter of becoming one with the machi—AAAHHHHH!
The rivalry between Lugnut and Shockwave during "Endgame". Special mention goes to near the start of Part 1, when after some jibing from Starscream, Lugnut moves in front of Megatron punting Shockwave offscreen in the process.
Megatron: Can't you shut [Arcee] up? She makes Blitzwing sound like he's got his head screwed on straight...
Starscream: Y'see, now he even likes Blitzwing better than you. Hmm... *Shockwave meanwhile has walked back onscreen*
Lugnut: *Slaps Shockwave back offscreen* NO! I am the most faithful!
Shockwave: *Walks back onscreen* Have you blown a diode?! I'm trying to work here!
The best part is when they get into a scuffle, and you can hear Shockwave yell "Liar, lying liar!"
Finally, while the two do get over it and work together, Lugnut falls over. Shockwave, one of the most stoic and focused of all Decepticons, points and laughs at him.
Pretty much all of the shorts animated by Studio 4°C are hilarious. Here are some examples.
"Career Day" has Optimus Prime introduce himself to a group of schoolchildren, but one of them (Daniel Witwicky) keeps pestering him with questions like how he's able to see when in his vehicle form and where his head goes when he transforms. In addition, all the children really want from Optimus is to turn into his firetruck form.
In "Explosive Fist", Lugnut keeps on punching the ground until it creates a huge empty pit. Blitzwing then comes over in his "Random" persona and tells him that he thinks the pool would look better over there, much to the Decepticon's annoyance.
"Starscream Heckles Megatron", as its title would suggest, consists of Starscream making fun of Megatron behind his back while he's making a speech. Starscream avoids getting in trouble by acting innocent whenever Megatron turns around, but when Megatron catches him Shaking the Rump, Megatron blasts him in the ass!
"Operating Table" has Sari help Ratchet perform surgery on Bulkhead. When Bulkhead recovers, he asks about the pile of leftover parts. Ratchet responds by shoving them down Bulkhead's throat, then walks off while whistling the Transformers theme song.
The 2008 Botcon script reading "Bee in the City" is the funniest thing this troper has ever seen/heard, full of shout-outs and fourth wall breaks aplenty. Watchithere.
The fact that David Kaye is getting to have both of his Transformers roles interact with each other in one place is both this an a Moment Of Awesome. Just the fact they're so far off from each other in terms of morality, yet have the same guy playing them, is amazing in and of itself, not to mention extremely meta.
The entire segment where Shockwave explains what happens when they face a cosmic-powered supervillain, including what the secondary characters do and Optimus Prime's reaction to it.
Optimus Prime: Nnnnnno, we won't be doing that.
Vangelus' entire performance as the "morally ambiguous" Transtech Shockwave is brilliant.
The Lampshade Hanging and Hand Waving of Professor Sumdac having a different voice (being played by Marty Isenberg instead of Tom Kenny), where Optimus asks why he sounds different and Sumdac answers that he has a cold.