For the past 75 years, Kool-Aid(R) has been a staple of summer time rereshment stands (I sold a gallon or two myself in my day) and an American icon (Jim Jones, notwithstanding). An upstart, with the name of "Kool", tried to get a trademrk for "Non-alcoholic beverages, namely carbonated beverages". Kraft Foods Global Brands, LLC, the owner of the Kool-aid trademark, opposed the "Kool" registration.
Faced with an ocean of evidence (including 450,000,000 gallons of Kool-Aid consumed per year), the Trademark Trial and Appeal Board had no difficulty in sustaining the opposition (TTAB opposition #91186494) in a decision dated August 20, 2009.
The proponent of the Kool mark attempted to distinguish its proposed mark and product from the Kool-Aid line, but was unsuccessful. There were just too many similarities for the TTAB to swallow.