"Stretch" here is your typical elastic superhero, with a slight twist- his body actually can't stop stretching, so he uses a special gadget on his belt to keep it under control and limit how much it happens. When he turns the dial on it, his elasticity increases in proportion to how far he turned it. Although he can't control his elasticity on his own, he can control where on his body it happens, such as making his fingers, neck, limbs, or tongue elongate while the other parts remain normal.

He's FtM, but his stretchiness lets him elongate and expand his clit to the point that it's indistinguishable from a hyper cock... as more than a few sexual supervillains have discovered! His ultimate fantasies all involve using his stretchiness to partner with other heroes, such as his crush, Magnifica... he fantasizes about being her living condom or even pulled onto her body like a skin-tight costume.