Massively Confused Investors Making Conspicuously Ignorant Choices (MCI-MCIC) , by Michael Rashes (Journal of Finance, Oct 2001). The author notes that many investors in the 1990s confused MCI corp, the big phone company that is now dead. It had the ticker MCIC. So when news hit MCI, as would often happen, poor little MCI, which is totally different, would move, and then move back. A good exogenous experiment with stock supply curves.
Another example of a stock that moved for no real reason was Aksys (ticker ESPR, now dead), which rose steadily in 2003 because some idiot inadvertently bought lots of stock every day for a few months. It rose from 7 to about 19 in 2003, when the error was discovered, and this guy owned 67% of the company by accident. with MCI