The insight:
Can something as tasty, colorful and fun as ice-cream ever be scary? It can and it is to a sensitive teeth sufferer. For them, ice-cream isn't a source of delight, it's a source of pain. Pain leads to avoidance, which eventually leads to long-term aversion - in short, fear.
The solution:
Tell sensitive teeth sufferers who aren't using us that the fear of pain is now redundant. Sensodyne is the 50-year expert in relieving the pain of sensitive teeth. No more pain = no more fear of cold treats.
The idea:
Design a PR gimmick around a newly-created horror mascot, The Ice-Cream Man.
Teaser phase:
1) Viral sites like Metacafe and YouTube begin hosting videos of unusual sightings: a person dressed in an ice-cream man uniform is going around scaring unsuspecting passerby and shoppers (all planted, of course)
2) Days later, print ads disguised as newsflashes tell of the "victims" of The Ice-Cream Man. These people, all sensitive teeth sufferers, describe the pain they felt as Ice-Cream Man maniacally serves them cold treats like Vanilla Strawberry and Butter Pecan.
3) An ominous-looking ice-cream truck (complete with a chilling melodic chime) starts prowling the streets. The headline on the truck reads:"He brings FEAR. He serves PAIN."
All teaser mediums lead our curious public to a microsite: www.fear_the_icecreamman.com
4) The microsite allows visitors access to all the newspaper clippings and Youtube spots plus additional eyewitness sightings of the Ice-Cream Man page, perhaps?) Most intriguing is a countdown clock on the site, with this headline: Relieving the fear of the Ice-Cream Man in: XX DAYS XX HOURS XX MINUTES XX SECONDS