Pepsi's lawyers... found experts to testify... that "the mouse would have dissolved in the soda had it been in the can from the time of its bottling until the day the plaintiff drank it," according to the Record. (It would have become a "jelly-like substance," according to Pepsi, adds LegalNewsline.)
Typically, it's Marketing which asks Legal to approve edgy communications. They would have been well served to do the reverse in this case.
That said, PepsiCo is quite lucky that this case is for Mountain Dew and not for some other beverage, say Lipton Brisk, or Diet Pepsi.
Smokers don't smoke for health benefits, and neither do drinkers of Mountain Dew. Dew drinkers already know that it's bad for them and, as such, this PR "problem" is unlikely to change the long term behavior of current drinkers.
The Mountain Dew brand has spent the last couple of decades attaching itself to action sports and all things "x-treme." And action sports athletes are always trying to do tricks that are new and more creative--things which are usually more dangerous.
Mountain Dew's ability to dissolve a living creature might ultimately be additive to its brand. Teens may view it as a valuable feature of the soda as they jockey, on the halfpipe, for status and manhood.