Clippy is quite cleverly hidden in Office 2013 but once you know where he is, he is quite hard to overlook.
Did you find him already?
Clippy is hidden in the “School Supplies” background of Office 2013. You can select these backgrounds when you logon to Office 2013 with your Microsoft Account in the top right corner.
Once logged in, choose File-> Office Account and select the “School Supplies” Office Background.
The paperclip on the left is shaped like Clippy.
With the Light Gray or Dark Gray theme, Clippy may be more easily recognizable.