The early Fallout games didn't really handle "main" and "side" quests in the way that your modern post-nuclear RPG does. At the start of the first two games you were given a vague, long-term objective to find some MacGuffin (a water chip, a GECK). From there, things just sort of happened. Things like becoming a porn star, defending towns from Mad Max rejects, or helping MacGyver sell antiques.
That's how you wound up with inspiring quest names like "Rescue Tandi from the Raiders." This was one of the first side quests in the Fallout franchise, and about as innocuous as a good deed can get in the land of Super Mutants and giant scorpions. Well, it should have been, anyway.
Tandi, you see, was the daughter of Aradesh -- chief of Shady Sands. When she was kidnapped by the local raider gang, the Khans, her father asked the first Fallout's protagonist for aid. Thus sealing her fate and that of the entire West Coast.
Inspired by the Vault Dweller's bravery, Aradesh, Tandi, and the latter's ex transformed Shady Sands into the New California Republic. Because nothing screams "thank you for rescuing me" like creating an imperialist nation that spreads faster and farther than a rumors of a cheeseburger in the post-apocalyptic waste.
The NCR, under the guiding and eventually quite wrinkled hand of President-for-Life Tandi, has its bright spots. It offer stability and relative safety in place of, y'know, almost certain death. The problem is that this "offer" is mandatory for anyone the NCR decides it applies to. That is, anyone with stuff that they want.
By the time of Fallout 2 -- around 2241 A.D., to be specific -- the NCR had annexed the technologically advanced Vault City under its crusty thumb to take advantage of its high-quality medicine. Thirty-nine years later, during the events of Fallout: New Vegas, the assemblage had swallowed up most of the Western United States.
What's interesting (i.e. worrying) about Tandi's actions are the spin they put on any side quest completed in Fallout. Saving a 16-year-old girl from club-waving mouth-breathers seems about as straightforward as it gets. Three games later, however, that small choice had massive consequences that ruined the lives and cultures of countless settlers trying to eke out an already harsh living. But, sure. You go ahead and rescue that girl's lost cat. Just be sure that cat won't grow up to be the next feline Hitler.
Slightly less existentially worrisome than Tandi, but twice as creepy, is Fallout 2's Myron.
Myron was a teenage sex-fiend and journeyman chemist. In this way he's indistinguishable from everyone else his age. What makes him such a grade-A creeper is how he goes around telling everyone about it.
As the creator of the Fallout-branded methamphetamine stand-in, Jet, Myron has quite a high (haha, get it!?) opinion of himself. He leverages that arrogance into some of the creepiest dialogue any Fallout game has ever employed. Specifically if you're playing a female character.
Dialogue like "What can Myron do to, ah-uh, for you?" Or just flat-out asking if you're one of his employer's "new whores." What's worse, if you roll a low-intelligence or low-endurance avatar Myron will take his disgusting self to new depths, and attempt to drug you with spiked drink of his own making.
Unfortunately, you'll very likely need to interact with this pallid lothario in a number of side quests. His darling Jet is highly addictive, even to the player. Several wastelanders are addicted as well, and only Myron can provide the cure.
Once he's outlived his usefulness nobody could possibly blame you for doing away with Myron personally, but there's a catch. While the creepy dealer looks like a grown adult in-game Fallout 2 doesn't consider him as such. Murdering the mouthy punk will instantly "reward" players with the Childkiller Perk, which reframes his earlier actions in an even more disturbing light.
Doesn't exactly reflect well on you, either.