Marvel: Ultimate Alliance

Iron Man and Silver Surfer are unlockable stikers in this game. To unlock them, you need to go to the S.H.I.E.L.D. simulator and play each of the four minigames 11 times. After that, a "Complete" message will appear in place of the number of times you have played that game. To unlock Iron Man, complete three minigames, and complete the other one to unlock Silver Surfer(a "Character Unlocked" Message will appear). You can then use them in any mission.

The Thing is an unlockable character in Marvel:Ultimate Alliance for GBA. Here is how to get his great strength in this game! First, you need to go to the Omega Base level. Once you get done talking to Dugan and enter through the door to his left, you will encounter some enemies. Defeat them, then go as far up against the wall as possible. Walk to the right, and you should eventually see a doorway.Go inside, and you'll find The Thing and Bruce Banner. After you finish talking to them, the "Character Unlocked" message will appear. On your next mission, you'll be able to select The Thing!