Final Fantasy XI didn't have any spawns quite that rare, but it still managed to pull some real world spawn bullshit. For example, consider Noble Mold (what is it with rare fungus monsters?); not only did it only spawn during double water weather in one zone, but this weather only came part of the time, at random, in one season in the in-game year. There were NPC weather forecasters, but they were worse than useless, because they weren't accurate but there was no warning of this, and most players wouldn't have spent enough time caring about the weather prior to this to notice. Even during the correct weather, it only spawned after 9-12 hours or so, and only if the (unmarked) placeholder mob was completely undisturbed the entire time (the placeholder morphed into the mob). Meaning that if some random idiot even so much as aggroed it, the timer would reset.
And since the game had no open-world PvP, there was absolutely nothing you could do to stop people from aggroing the placeholder. Naturally, if you attacked it, it would be claimed to you, but that would make it useless for spawning purposes. Of course, that meant that other players could grief you by deliberately holding the placeholder. You couldn't even rely on talking to people, because the same servers were used for the entire world including Japanese, French, and German speakers, and the "auto-translate" (basically a phrasebook) didn't have any terms to explain monster spawning mechanics because they were supposedly secret. For the same reason, attempting to call a GM on people who griefed you by deliberately killing the placeholder would just result in a stock response about how "we can't reveal game mechanics to players". And finally, the item drop wasn't even 100%! I knew a player who had to kill it 5 times to get its stupid hat (no achievement or even a title awarded).
Noble Mold wasn't the only such "live spawn" monster either, but its weather mechanic made it one of the worst. Voluptuous Vilma was another bad one, but mostly because it was the one-and-only double live spawn meaning that you had to let an (again, unmarked) normal monster called Overgrown Rose stay alive and undisturbed for up to 12 hours to morph into an elite mob called Rose Garden, then let that stay alive and undisturbed for another 12(?) hours to morph into Voluptuous Vilma. Again, no achievement or title awarded, but at least its drop was apparently 100%. I say "apparently" because the same item dropped off the intermediate spawn at a 5% or so rate and the hassle of keeping a monster alive in FFXI meant that most people just did that instead. I personally do not know even one single player no matter how literally autistic who even tried spawning Voluptuous Vilma. Even the name was a lie; it wasn't some hot girl, but a big green tentacle monster with bad breath.