Social media reacts to Mike Leach, K.J. Costello and Mississippi State Bulldogs upsetting LSU Tigers

Mississippi State's Costello cooks defending champ LSU for 5 TDs and 623 yards (2:19)

K.J. Costello throws for five touchdowns and 623 yards as the Bulldogs upset the No. 6 Tigers 44-34. (2:19)

Welcome back to the SEC Mike Leach. The new Mississippi State Bulldogs coach upset the reigning national champion LSU Tigers in his season debut.

K.J. Costello, the Bulldogs' quarterback, transferred from Stanford and was making his first SEC appearance. All he did was set the SEC single-game record for passing yards with 623 yards. He added five touchdowns in the 44-34 win.

After coaching stops at Texas Tech and Washington State, Leach was back in the SEC for the first time since being Kentucky's offensive coordinator in 1998 and social media loved it all.