In Jonathan Coulton's "Skullcrusher Mountain", a mad scientist has kidnapped a girl and is politely offering her slews of gifts, "romantic" outings, and other niceties in hopes that she'll stay.
Stephen Lynch has the song "Beelz", in which Satan introduces himself with, "My real name is Beelzebub, but you may call me Beelz!", and from there it stays super perky talking about things like enjoying bubble baths and hating how skiis don't work well on hooves.
Magnetman in The Megas' "Don't Mess With Magnetman" is part of Dr. Wily's plan for world conquest, and doesn't seem to have any problems with it, but his actual concern seems to be his affection for Roll, who may not reciprocate, but at least seems to regard him well enough to warn him to watch out because Mega Man is coming for him.
Sure, my dad wants to rule the world But can you let that come between us, girl?
Voltaire indulges in this trope frequently. For example, "Death, Death, Devil, Devil, Evil, Evil Song" is about a rather nice young man who cares for his grandmother, goes to church, and loves to play the guitar and sing... about death and devils and evil. Satan is his biggest fan.
", a mad scientist has kidnapped a girl and is politely offering her slews of gifts, "romantic" outings, and other niceties in hopes that she'll stay.