Lyric discussion by SnapJazzy 

Cover art for Mad Hatter lyrics by Melanie Martinez

Based on the lyrics, it's pretty self-explanatory. The whole song is really about her being crazy and how that's NOT A BAD THING.

"Skinny dip in rabbit holes for fun" "I'm peeling the skin off my face" "Getting drunk with the blue caterpillar"

All of those lines are dangerous things to do, but she doesn't care. She outright says "'Cause I really hate being safe." Crazy people, or insane people, are nuts (or mad) and don't want to be normal.

Compared to Alice in Wonderland, she doesn't want to be the normal Alice. She wants to be the Mad Hatter, the crazy insane free-spirited guy that goes through life as an insane person.