Mergers and acquisitions in 2015 were at an all-time high, surpassing their 2007 peak, according to Mergermarket. But nothing quite compared with Allergan’s (AGN) head-spinning M&A spree. In the span of one year it sold itself (to Actavis), kept its name but moved to Ireland, broke itself up (selling Actavis’s legacy-generics business to Teva) (TEVA) and announced the year’s biggest merger (its pending $160 billion megadeal with Pfizer) (PFE). Allergan’s shareholders might worry that the company was having an identity crisis, if not for the fact that the stock has returned about 19% over the past year, lapping the rest of the pharma industry’s meager gains.

This article is part of Fortune’s Best in Business 2015 package of highlights and lowlights of the year in business, politics and the economy by the writers and editors of Fortune. To see the entire package, click here.