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After Addison arrived to throw a wrench in Meredith and Derek's burgeoning love, we learned exactly what made McDreamy run across the country to get away from his failing marriage. And his name was McSteamy. Or Mark Sloan, to be more exact. Who will ever forget the indelible image of Eric Dane stepping out of Addison's shower with that tiny towel around his waist? It turned out that Addison had slept with Derek's BFF, who followed her across the country to try and convince her to return home before sticking around Seattle too. In the end, she didn't really want anything more from him than some booty and decamped for Los Angeles (and her own spinoff, Private Practice), making this the rare love triangle where the two suitors vying for the same person wind up with a friendship when all is said and done. Mark and Derek built their bromance back up from the rubble and stayed that way until Mark died following season eight's plane crash.