As an undergraduate at Cal, I was working in a cell biology lab with fluorescent tags. These tags are fluorescent colors produced mostly by marine organisms and are used as markers that can be attached to a cellular component to see which areas of cell they are expressed in. However, the genes responsible for producing such fluorescent colors have already been identified. One can fuse these fluorescent genes with proteins to produce a glowing protein, which can then be tracked inside the body.
I had an idea–lets make fluorescent pets! I would scan various animals and identify a color that glows in dark. I would then identify the gene. I would then fuse the gene to the progenitor cells of a chihuahua embryo such that only its skin would glow once the dog was born. Then I would sell the puppies to scandalous people like Paris Hilton and Britney Spears. All I would need then would be ONE cover picture in a tabloid magazine and America would be demanding the puppies that glows in dark! Hell yeah!
Seriously, it can be done. In fact it has been done. A Korean Team of scientists used cloned cats with fluorescent protein. Of course they made those glowing cats to explore newer ways to cure human diseases and not to appeal to American celebrities. But that can be done. Anyone interested?