The LEGO Marvel Super Heroes theme (Exclusive Minifigure: Iron Man & Captain America 2012 Collectors Preview) is based on the characters created by Marvel Comics. Originally Marvel was a subtheme of the LEGO Super Heroes theme but was later separated into its own theme. Over time, sets in the Marvel Super Heroes theme includes most characters and situations released to the marvel Universe from films to the comics to TV series.
2012 LEGO Sets
2012 was a very important year for LEGO license themes, namely, the contract with Lucasfilm was renewed to extend Star Wars sets until at least 2022. The LEGO Group also celebrated its 80th anniversary in August of that year. 2012 also marked the year for one of the largest number of new and important themes being released which included The Hobbit, The Lord of the Rings, Marvel Super Heroes, DC Super Heroes, Monster Fighters, Friends and LEGO Friends. With the introduction of all these new themes LEGO did discontinue a number of beloved themes in 2012 which included Alien Conquest, Atlantis, Pharaoh's Quest, Kingdoms and Harry Potter which did make a return six-years later, thankfully.