To make fun of both black people and Dragon Ball Z, the image of Cell near exploding in self-destruction was photoshopped commonly to color his face pitch-black, along with bright red lips in parody of early comics featuring black people(in obviously racist stereotypes) like those of Winsor McCay(best known for Little Nemo).
Because of the abnormally fast speed of 4chan's /b/ board, users will commonly photoshop multiple images and upload them to a particular thread in fast succession, creating a short narrative to give the sense of progression and timing to a particular image joke. The original ordering that got people lollin' was Cell with his mouth open proclaiming "SHOOP DA WOOP", a meaningless but intend-to-be-racist chain of black slang, then either a bloated Cell about to explode saying "OOPS I SWALLOWED MAH LAZER" or the wide mouthed beam-firing pose of "AHM FIRIN' MAH LAZER!!!1". Spellings may vary, but imply a Southern drawl.
The open mouth beam firing became the final evolution of the meme and is thusly shopped onto other faces or in new situations using wordplay of the original three or entirely new lazer-free shops.