With shares of Starbucks, Campbell Soup and PPG Industries now the targets of high-profile activist investors — and the rest of the market in a tailspin — CNBC's Jim Cramer wanted to make sure investors weren't getting ahead of themselves. On Tuesday, hedge fund Pershing Square, run by Bill Ackman, announced a $900 million stake in the stock of Starbucks; Nelson Peltz's Trian Partners disclosed a $690 million stake in shares of PPG; and Daniel Loeb's Third Point raised its existing stake in Campbell Soup's stock.