Bill Ackman just took a massive stake in Chipotle and wants to shake things up (CMG)

Bill Ackman wants to shake things up at Chipotle.
In a regulatory filing on Tuesday, his hedge fund Pershing Square disclosed a 9.9% stake in the fast-food chain, and said it is seeking talks with the company.Shares of Chipotle jumped following the news. Ackman's stake makes him the second-largest shareholder in the company."The Reporting Persons [Pershing Square] believe that the Issuer’s Common Stock is undervalued and is an attractive investment," the 13D filing stated.