2009 - The Undertaker returns to attack the new World Heavyweight Champion CM Punk
2010 - Daniel Bryan returns to help Team WWE fight The Nexus, Undertaker returns to confront Kane
2011 - Kevin Nash returns to screw CM Punk out of the WWE Championship
2013 - Triple H turns heel and costs Daniel Bryan the WWE Championship
SummerSlam seems to be the pay-per-view where we get a few surprises and twists, do you think there's any chance we'll see one this year? Perhaps a swerve could see Seth Rollins cash in Money in the Bank, or a surprise appearance from someone like Sting?
PS. I just hope the 'shock' isn't Cena retaining the WWE Championship against Brock Lesnar.