15He Originally Had Red Hair and No Connection to Thor
As we said, the modern day incarnation of Loki debuted in Journey into the Mystery #85 when he revealed as Thor's half-brother and began a long tradition of trying to kill Thor and play with his cool hammer.
His cosmic meddling would famously a few years later, similar to his role in the MCU, cause
the formation of the Avengers. However, Loki appeared in comics well before any of that and actually predates the earliest of Marvel's heroes by over ten years.
Sporting a red crew cut and pink costume (outfitted with epic shoulder pads) the God of Mischief's first true appearance came in 1949's Venus #6. Published by Timely Comics -- the future Marvel - this comic series followed the romantic adventures of the Greek Siren Venus which naturally brought her into contact with some of mythologies greatest characters.
For his part, Loki is depicted as the ruler of Hades, having nothing to do with his Norsian background or Asgardian lineage. When comics made way for the era of superheroes, Loki was reimagined by Stan Lee and Jack Kirby as the trickster we all know and sneer at today.