Adventure Comics #338 was the debut, and originally the only appearance, of Glorith, the Time Trapper's henchwoman. When she first appears in his lair, the Trapper tells her to come closer so he can whisper his evil plan to her. In literally the next panel, the Trapper is doing exactly that and Glorith is congratulating him on creating such a wicked scheme.
After the Legionnaires are accidentally turned into infants, the Trapper attempts to use this to his advantage by manipulating the kiddie Legionnaires into committing crimes for him. And then it hilariously backfires on him when Element Lad turns his rocket into candy... which the Legionnaires start eating! Stranded on a deserted planet with the Legionnaires, the Time Trapper then comments things couldn't possibly get worse.
One of the most entertaining elements of the Legion's original stories was the sheer number of teenagers who tried out for the team with powers that were utterly ridiculous. Including the likes of Polecat (who emits a foul smell from the horns on his head), Eyeful Ethel (with a ring of eyes growing around her head), the Mess (a kid who can attract dirt), Calamity King (who possesses the power of bad luck), and an unnamed kid who could turn things green. In fact, Calamity King becomes a Brick Joke when Star Boy ponders if his expulsion from the Legion was instigated by his contact with the aforementioned reject, and during the Five Year Gap the Legion's ultimate dissolution was preceded by Calamity King getting accepted while they were desperate for members.
Matter-Eater Lad meets fellow Bismollian hero Calorie Queen, whose powers are honestly better than his, because the more she eats the stronger she gets.
Matter-Eater Lad: I know you. You're Taryn Loy, the daughter of Bismoll's most brilliant atomic scientist!
Calorie Queen: And YOU, Matter-Eater Lad, are Mr. Useless!
The teenage Legionnaires decided to start Legion try outs again, which of course introduced us to some people with phenomenally terrible superpowers, like X-Bomb Betty (Who can explode once, and only once), Plaid Lad (who can turn all fabric into plaid), Accordion King (whose lower half seems to be an actual accordion and who came to the try out with his mother), and Barber Boy (who's got a pair of scissors for a hand and can fire "Mousse Vision" from his eyes). Some things never change...
Every issue where Matter-Eater Lad was the main character, starting from when he has to be Polar Boy's lawyer in a rigged trial to when he overthrows Prince Evillo's tyranny and marries Saturn Queen.
In issue #11, Tenzil's the star of an archaeology program where a crew has discovered what we recognize is remnants of the Batcave. Tenzil instead believes they're proof of a race of gigantic presidents who used to roam the Earth.
In issue #14, Tenzil frees all of Prince Evillo's undead wives from the underworld, and they promptly make it clear they are running things now. When they reappear as brainwashed servants in #49, one wife snarks they still won't do windows.
Issue #49 opens with Tenzil having a dream about all the Legion's greatest villains doing a telethon to raise money to repair the now destroyed Earth, including the likes of Mordru and Starfinger in tuxedos and top hats singing about Earth.
The sheer irony in that Polar Boy, who had tried his hardest to be taken seriously as a hero and was the only Sub to be officially made a Legionnaire, is treated as a Butt Monkey during the Five Years Later stories and spent two years in jail for rioting at a pizza place. And that the Subs, who were mostly viewed as a joke during the Pre-Crisis era (save for Night Girl), became a bunch of respected and hardened badass commandos fighting Earthgov. Seems the only Sub whose respect levels remained consistent over the years was Night Girl.
Followed by Brek finding himself the leader of a group that could be considered the Subs for the original Subs, consisting of two horny devilish teenage girls (Styx and Stiletto), an insurance saleswoman who can literally get you to buy any policy she wants you to (Policy Pam), a zombie who magnifies echoes (Echo-Chamber Chet), a board game enthusiast (Spaceopoly Lad), and a reformed villain whose power is his capacity to inhale and exhale (Sugyn, a literal blowhard).
Chameleon Boy and Computo II did not have the easiest relationship in Legionnaires. In one memorable scene, Reep bumps into Danielle while she's trying to steady a hot cup of coffee, and Reep accidentally makes her spill the entire thing on her (mostly white) uniform. Danielle just stands there, looking like she's about to explode, her midsection covered in stains, and thinking about wanting to execute Reep. By hanging◊.
Jo Nah (Ultra Boy) finding himself stuck between unwanted advances from two different women. Spider-Girl, who won't take a hint, and Veilmist, who keeps trying to get Jo to kill her husband Firefist so they can marry.
When it's down to Devlin O'Ryan to fight Mordru, after he's taking down the rest of the Legionnaires, Devlin gets his attention by saying he'd gotten friendly with Mordru's harem of wives. Mordru loses his shit like you wouldn't believe.
Post-Zero Hour continuity
This conversation, during the Bizarro Legion story:
Invisible Kid:You lick it! Live Wire:You lick it! [beat] Invisible Kid: ...Ferro, come over here. Karate Kid: Now that's just wrong.
Gates in the twentieth century, volunteering at a soup kitchen. "Human! Step forward and claim your sustenance!"
Chameleon and Infectious Lass in Gail Simone's "For No Better Reason" arc:
Arrow:[weakly] I'm... I'm willing to die for my cause. Chameleon: Oh, you'll die. We'll all die someday. The issue is, do you want to die in bed, surrounded by your loved ones... or bent over in this alley with a woefully inadequate supply of tissues?
Tenzil trolling Chuck in the issue where Sensor (Princess Projectra who, in this continuity, was a human-sized alien snake) is inducted as a member. Tenzil informs Chuck he has to do a special order because Sensor's people are carnivores by nature, and primarily prefer to dine on large, plump mammals. Chuck coughs up his smoothie all over Tenzil's face. Tenzil says it was worth it.
The Athramites spent every issue they appeared in ruthlessly trying to get the Legionnaires to experiment with their costumes and wardrobes... and then they met Monstress. By the end of their first session, they were literally begging her to settle for a single pair of gloves after hours of redesigns when she declared they were "Finally making progress."
And on her end, Candi has absolutely no clue the Athramites are completely terrified of her. After Element Lad changes her skin coloring from green to orange, he innocently sics her on the Athramites by suggesting they can work with her new skin tone. Candi eagerly declares "Yes, let's do a whole new wardrobe!" The Athramites run down the halls screaming in abject terror.
Shrinking Violet, while under the Emerald Eye's control, tried to brainwash the Legionnaires. Somehow, Gates managed to shrug off the brainwashing long off to go on another political rant. Kinetix responds by turning him into an egg.
The realization that Chameleon's costume is actually part of his body... meaning he's been walking around naked the whole time.
When the Science Police do a raid on Legion headquarters, they burst into Element Lad's room. Jan, who at the time is totally naked, takes the whole thing in complete stride. Then one of the officers finds an extremely foul smelling animal Jan acquired as a pet on a previous mission. While he's explaining "Tulip's" eating habits, the officers flee the room like their lives depended on it.
Lightning Lord threatens Tenzil Kem. Tenzil Kem bites off Lightning Lord's finger.
The Subs invading the JLE's satellite with a high-jacked school bus.
"Hit the brakes! THE BRAKES, NOT THE GAS!!!!"
Chlorophyll Kid now believes he can hear plants talking, which may or may not be true, and proclaims vengeance on the JLE for not watering their house plants.
Golden Boy: I see the Subs' green thumb is as delusional as ever.
Fire Lad: So Chlorophyll Kid thinks he can converse with your house plants, so what?! We all have our shortcomings!
The three Brainiacs arguing with one another, mostly instigated by Threeboot Querl's refusal to work with an adult version of himself and accusing Brainiac 5.1 of being a suck-up. He muses the Reboot Legionnaires must be slaves to adults in their world, to which 5.1. retorts that his cynicism is a sign of a lesser-grade intellect.
Threeboot Querl: Oh why don't you get a haircut?!
Retroboot Querl: I'M VERY BUSY!
When Blok compares his relationship with the White Witch to Widlfire's relationship to Dawnstar, and then compares them to Romeo and Juliet, both are in agreement it's the worst love story ever.
On a mission to Polar Boy's homeworld Tharr, which is supposedly the hottest inhabited planet in the universe, Sun Boy tries to impress two local girls with his power. Which is heat generation or, as he puts it, "I make things... hot." On the hottest planet in the universe, Sun Boy learns that is not an amazing power.
In Action Comics #864, Batman and Lightning Lad more or less spend the entire issue fighting over Superman's attention like Betty and Veronica fighting over Archie. When Batman asks to speak to Superman in private, Garth complains how he doesn't understand what's so interesting about Batman like how he wears a mask (and that not even the bad guys from his time wear masks). Superman briefly points out he's forgetting Persuader.
A couple of pages later, Garth is muttering to himself about how Batman can't even fly despite his name.
Phantom Girl doing an impression of "Serious Shadow Lass," clenched fist and all, when she recalls Tasmia justifying sleeping with EARTH-MAN.