The Fantastic Four gain their superpowers when a cosmic ray burst hits flight researcher Reed Richards’s spaceship (instead of, as one might expect, broiling them instantly). Richards’s body turns to plastic, and is able to stretch into any shape. Fortunately for him, and the other members of the Fantastic Four, the inner lining of their spacesuits transform with them, so they each have something to wear.
Spandex might help clothe a real-world Mr. Fantastic in a pinch. It can stretch up to about twice its original size, depending on the thickness and weave.
U.S. and Korean scientists in 2012 discovered a super-stretchy, super-strong hydrogel, a kind of polymer soup suspended in water. Think super-tofu. The stuff can stretch up to 20 times its starting length and can absorb a lot of energy before tearing. Doctors might be able to use it eventually to help people regrow cartilage.
Even if they could make a suit out of the new hydrogel, Mr. Fantastic might still want to wear a plastic fig leaf -- the material in the September 2012 Nature study was see-through.
Left: Fantastic Four, 2005.