This is a small page demonstrating the blue Samus glitch. One can find more information by visiting GameFAQ's Super Metroid FAQ page.
I've once managed to actually diagonal dash behind Mother Brain, but without the infant metroid stuck somewhere she couldn't hit, the story continued, with her backing into Samus, knocking her in front of Mother Brain. I'd be interested to know if anyone has a save state of Samus behind Mother Brain and the infant metroid stuck in a place Mother Brain can't reach.
Kuwanger.net - Sort of like stag beetles in tubes.