Marvel Comics vs DC Comics
Connection:
Both are green-themed comic book villains who utilize illusions against their enemies
Both a rough life growing up (Quentin Beck had a love of special effects and movies until his father smashed his first camera projector. New 52 Jonathan Crane was bullied as a kid so he wanted to terrify others by using fear while Prime Earth Crane ended up being trapped in chamber for days after his father died of a heart attack)
Both are very skilled chemists and wore "masks" which they can use to intimidate others
Both were part of a superhero's rogue gallery (Spider-Man and Batman respectively) and joined a villainous team (Sinister Six for Mysterio and Legion of Doom for Scarecrow)
Both had a job but was taken away from them (Quentin was blacklisted after one of his actors was burned. New 52 Crane fired a revolver from his class which caused him to be expelled while Prime Earth Crane was suspended from collage performing habituation on a student with arachnophobia by pouring a bucket of live tarantulas)
Both are also "masters" of something (Scarecrow wants to become the "master of fear" while Mysterio became the master of special effects)