In fact, sellers TPG Capital, Bain Capital LLC and Goldman Sachs Capital Partners did have it their way, making off with 5 times their initial $620 million, 7-1/2 year investment, including dividends.

But the buyout also pushed the limits on tactics. Burger King was the first acquisition taking a public company private that filed both a tender offer and, as a backup, a traditional merger agreement. "This has to be one of the most unusual deals both because of the structure [and because the Burger King sponsors] only were serious about this from the very end of August," says Holland & Knight LLP attorney Kara MacCullough, who along with Laurie Green represented Burger King. "They went very quickly from doing a dance to being married in about a two-week period."

For years tender offers were simply not used in take-private acquisitions because of the "best price rule," which the Securities and Exchange Commission passed in 1986 to ensure that all shareholders got the same price. The SEC revised the rule in 2006 because varying interpretations made tender offers unattractive. Recently, however, buyers have grown more comfortable with tender offers: Six private equity-sponsored take-private tender offers occurred in 2010, according to data from Weil, Gotshal & Manges LLP, five in the second half.

In the Burger King deal, attorneys and bankers added layers of complexity, conducting the go-shop period and marketing the debt concurrent to the tender offer and merger agreement processes -- all of which needed to be resolved by year's end. The starting gun sounded with the deal's Sept. 2 announcement, leaving little room for error.

Burger King filed its tender documents first, in which 3G would pay $24 a share in the hopes it would get the 90% necessary to complete a short-form merger. This is tougher than it seems in a widely held public company, and thus not commonly used. "It's quite unpredictable," says Stephen Fraidin, veteran corporate lawyer for Kirkland & Ellis LLP who represented 3G.

There were three private equity sellers, creating uncertainty about whether they'd be on the same page. Moreover, collectively they only owned 31.5% of the company, the rest held by a wider shareholder base. From the lender perspective, in this case J.P. Morgan Chase & Co. and Barclays Capital, committing to a tender offer is tricky: While 3G might have been able to get more than 50% of shareholders to tender, forcing the buyer to complete the purchase, it might not have been able to get the requisite 90% to close the short-form merger. In a nightmare scenario, a lender would have committed to a deal the buyer couldn't complete.

The driving force behind the so-called parallel structure was banker Robert Kindler, global head of M&A at Morgan Stanley, which advised Burger King. Morgan Stanley managing directors Carmen Molinos and David Ciagne led the deal, but Kindler, an M&A lawyer at Cravath, Swaine & Moore LLP for 20 years before turning to banking, had long believed PE firms shouldn't be afraid of tender offers over fears that they wouldn't garner enough shares.

He told Lazard bankers, who advised 3G, they could also get a top-up option, which allows a purchaser that is falling short of the 90% to buy up newly issued shares of its target to reach that proportion. "I was sure we could get to 90% without the top-up option," says Kindler. "With the top-up option, it was a virtual certainty."

But 3G would still need Burger King shareholders to tender 79.1% of their shares (usually this can be 50%) because the fast-food chain didn't have any more registered stock to issue. Thus, there was a Plan B, the traditional one-step merger, where shareholders vote at a meeting, a process that takes several months longer than a tender offer. Burger King filed its merger proxy Sept. 24, one week after its tender documents.

Lawyers say that from now on, whenever a company lacks enough registered shares to issue in a tender offer, the Burger King parallel structure may be used. Sure enough, Gymboree Corp. replicated the parallel structure the following month in Bain Capital LLC's $1.8 billion buyout.

As a result, Burger King proved to be something more than your run-of-the-mill buyout. As Fraidin says, "It's one of the most interesting deals I've ever worked on."