Tony Stark's Backpack

Tony Stark's Backpacks are actually self-attaching prototypes of the Mark I and Mark II.

Capabilities

 * Transformation: The Backpack can transform into the Iron Man Armor within exactly 20 seconds.
 * Durability: The pack can withstand all kinds of punishments in Backpack and Armor Mode.
 * Anti-Gravity: The backpack has a built-in anti-gravity generator. This allows the suit to be a lot less heavy compared to the normal one.

History
Tony Stark invented this backpack during the time of Ancient History 101, so he can change into Iron Man whenever and wherever he wants. It has anti-gravity tech inside so the armor doesn't weigh too much.

Stark eventually made a backpack for the Mark II armor by the time of Enter: Iron Monger and field-tested it for the first time in the same episode.

Trivia

 * Tony's backpack is similar to his briefcase from the comics except Stark donned the suit manually instead of automatically.