Origins

It was originally believed that Reed Richards (Mr. Fantastic) transferred all his knowledge in to Big Brain when he went in to hiding after the death of his wife, Susan Storm (Invisible Woman). However, it eventually becomes apparent that Reed Richards is controlling the Big Brain robot remotely. When Big Brain goes offline, the remaining members of the Fantastic Five, aswell as Stinger travel to the source of the remote controlling to find out what happened. They find the origin to be in the Stinger and are attacked when they arrive. They eventually find Reed and he reveals that Susan is indeed still alive, and being held in suspended animation so that she can hold together holes in reality while staying alive. Reed refuses to return home as he wants to find a way of bringing Susan back to life first.

Suits

The original Big Brain suit was not humanoid at all, and looked more like a periscope. It was believed that this was because Reed blamed himself for the death of his wife and did not see himself as human anymore.

The second suit, after the first was destroyed was the better known, humanoid one which resembles an alien.