I suggest the Rare Candy as a starting point

Do you mean, have a rare candy be part of the story? Or are you recommending I look at something called “Rare Candy”

The former.

Not really a pokesona, but I'd be happy to tf into a Lycanroc, Zeraora or other pokemon to try out that move. Though it's more fun if the HM disc is scratched out or dirty, and being able to read only the last letters it looks like it's the move "cut".
Trying to cut some trees with the new ability turns into ripping them off the earth with impossibly large muscles :3

Now that’s something I can work with~

Oh boy Pokemon Theres a lot of potential.
A rookie defeating higher leveled champions by accident with an ilegal TM. Causes compuond growth with the move and the EXP gain.
Jirachi accidently gives a weak Pokemon a monkey paw wish
Pokerus and effort values plus good IVs causes a Glitch in the system/reality and hulkout move IS now a thing.
Weak move that no one uses "hulkout" but infinite PP scheme leads to stacking results.

Have fun!

Trainer finds a golden Lucky Egg, giving WAY more extra EXP than intended?

Oooh man this sounds fun. I'm picturing my pokesona Andre' giving a little demonstration to a friend of the move "Bulk Up" but not realizing he's standing close to a Dynamax power well that's just overflowing with energy and "Bulk up" quickly becomes closer to "hulkout".

Or maybe a friend spikes his drink with a few too many hyper potions and rare candy's... Plenty of fun options

Lopunny finding an evolution stone, and long story short, she gets way more than she bargained for.

I admit, this comes from a comic made by "Outlawmonkeyx", also known as "Outlawg", the maker of the Muscle Mobius comic series, but your journal made me think of it.

Basically, a hungry Pikachu decides to grab some fruit from a nearby tree, but those apples (or whatever berry they're meant to be) have a different effect than expected...