The "Think!" theme for Merv Griffin's 'Jeopardy' game show is one of the more memorable pieces of game show music in history. Composed by Griffin himself, "Think!" is one of those catchy ear worms that crawls in your head and just won't quit. The show, hosted by Alex Trebek, has been on the air since 1964, giving us almost 50 years of thoughtful quiz show entertainment.