Captain America: Puny Steve Rogers was injected with the super-soldier formula to become the US military's secret weapon in World War II. Frozen in the ice following a fall into arctic waters, Cap was thawed out years later and immediately inducted into the Avengers, where he quickly became the team's leader.

Iron Man: After building his high tech suit of armor to help him escape captivity, billionaire industrialist Tony Stark improved on his designs to become a costumed hero. Teaming up with like-minded heroes to form the Avengers, Stark is also the team's main financial backer.