FAQ

Dr. Banner was supposed to be working on a serum for a band of super soldiers, but was instead working on a serum for him to be able to control the Hulk. After rushing in to the chamber and using the serum ,Banner was able to control the Hulk for a short time, Hence the talking and later reverted back to the regular Hulk.

The ax/hammer hybrid primarily wielded by the character is considered to be the "Ultimate" version of Mjolnir, as revealed in Ultimate Power #9. However in the Ultimate Thor miniseries it is revealed that the original axe hammer is no longer necessary, as it's not the real Mjolnir but instead, Dr. Braddock gives Thor tech-armor, and Thor suggests to turn the power supply into a hammer. It is stated that this version of the hammer is not restricted by the worthiness test. Even when Thor wielded the true hammer Mjolnir, the Earth #1610 version did not have an enchantment making it unable to be used by the unworthy. It was stolen and used several times by various villains, Magneto, Gregory Stark and by Captain America. When the Children of Tomorrow slaughtered the Asgardians, triggering the second Ragnorok, Mjolnir was hidden with Thor's son Modi in the Room with No Doors, in an attempt to keep it safe until Asgard may be restored to its former glory. Thor returned to Earth and he was given a Stark-enhanced version of the EDI power harness and the axe-hammer he wielded previously. Being really strong is all that is necessary to wield this ax/hammer version of Mjolnir, or having magnetic powers in the case of Magneto. But without the harness, you simply won't get the bang for the buck since they are technically a linked pair.