[Mazoku]

Magma from the New Mutants, Special Edition, where they have adventures in Asgard, was turned into a fairy/dark elf.

She's tricked into eating fairy food, which is something from classic folklore, which will get people trapped in the fairy world, or fall asleep, or become enchanted in some way, compelled to dance and party with them, becoming their servant, etc., often for many years or forever.

I haven't seen any explicit mention of transformation into one of the fairy folk from eating their food in any folk tales, though I have read the Unseelie, dark fairies of Celtic folklore, do whisk away people they encounter on dark and lonely nights and transform them into Unseelie like themselves.