Seeing Guy's muscle growing right in front of him had reawakened Cray's desire to be big - to be the biggest - and Cray was helpless to stop the ointment's effect: to give him the body he wanted.
Guy, unfortunately, was having quite the same problem. Seeing the clip with the Hulk growing on TV had triggered a new wave of muscle growth, and now that Cray had begun to grow as well, it was even more difficult for him to try and concentrate, to imagine himself at a more manageable size.
And thus it came that both Guy and Cray kept on growing: lats spreading wider and wider, quads thickening, and biceps inflating with size and strength. They needed to stop this - but what could they do?