Peculiarly, her cougar & even Bewitching [S|L] & Pharaoh [S|L] cat forms can roar, like four biggest cats: tigers, lions, jaguars, & leopards.
The game client's shop filters Nidalee as a Support despite her no longer having that tag as a secondary one.
Given that she's a wild child, it is unknown how Nidalee could've learn to speak languages fluently; since in real life, feral humans who learn their first language late in life never master such linguistic aspects like phonology, morphology, & syntax.
Nidalee was rumored to have a special stackable damage over time that could be applied by all her damaging abilities as well as Prowl granting her stealth for 2 seconds when leaving brush in cougar form (both effects actually existed and were removed prior to her release)
Nidalee used to have a bug where Primal Surge applied Swipe's damage (meaning she could kill her teammates if they were low enough).
Nidalee is one of the few champions to have an extra set of emote animations (taunt, laugh, and dance animations each for human and for cougar, without voice changes)