Retail investors loaded up on Apple last month as the stock plummeted to its lowest levels of the year and the company doubled its capital return program. So much so that the stock now has more ownership than ever in the history of TD Ameritrade, which tracks the largest pool of retail investors.

The general thinking on Wall Street has been that retail is the so-called dumb money and so one would think the stock garnered the most retail interest as it hit an all- time high of $705 last year. But that wasn't the case.