trust you've seen xkcd's take on the pot of gold at the end of the rainbow?
https://m.xkcd.com/1944/ Gold isn't created by normal fusion in the Sun though, it needs a supernova.
In Dresden verse though, you'd follow a rainbow through the NeverNever, to the pot of gold. Unless you just want a pot of ectoplasm when you get home, you'd need to open a gate into the Sun - which is at least a quick and painless way to die. However, you could then (in the middle of the blasted wasteland in the Never Never) have cooling gold, which could be collected by someone else.
So a sneaky, evil Leprechaun could spread rumours of having a pot of gold, allow himself to be 'captured' by a Wizard with no Scholarship, and lead them to the appropriate point in the Never Never. One instantly fried Wizard later - massive riches! The joy of it is, they aren't lying - they *are* taking you to their pot of gold.
Leprechaun should have Mythic Immunity to Sunlight, and possibly have received a death curse or 3.