Mythology buffs are sure to love American Gods, if they haven't already latched on to Neil Gaiman's novel. The story takes deities from all cultures and brings them together in the modern world. Some of them are more well known than others. Who is Mad Sweeney based on in American Gods? Pablo Schreiber's character is an obscure legend with a big personality.
No, he's not based on the Victorian penny dreadful character Sweeney Todd, unfortunately. As much as I think Bryan Fuller would do an excellent job adapting the "mad" demon barber of Fleet Street, that's not the tale we are attending.
This character is based on the Irish god Buile Suibhne, who is often called "Mad Sweeney" in translation. In the myth, Suibhne was a king and a warrior who was given a rock to protect. Just a rock. That drove him mad, which gave him a kind of power. Another part of the legend tells that Suibhne was cursed to wander after killing a cleric, and that he composed poetry as he traveled from place to place, unable to settle and trying to avoid his prophesied death. It's romantic and tragic, like the best legends should be. He also has jumping and flying powers, like a bird, which is pretty neat.
On American Gods, Sweeney is one of the Old Gods. He was brought to America from Ireland, has no accent, and is also technically a leprechaun — or that's a joke he has with himself. That sounds stereotypical, but may explain why Sweeney refuses to drink Guinness.
Sweeney isn't exactly lucky, but he is charming and has some magical talent according to a promo. He's pretty good at coin tricks, possibly better than most mortals. Without getting into spoiler territory, that knowledge of coins comes in handy when Sweeney meets Wednesday and Shadow Moon.
I'm not sure whether or not the poetry aspect of the original Mad Sweeney myth will come into play on American Gods. Still, it'll be interesting to see how this myth meshes with the others and contributes to the journey.