#2 Ace Steel taught him how to wrestle
It is a well known fact that CM Punk came up through the independent circuit, and because this was a special show, to commemorate the very last show at the historic Knights of Columbus, Punk may have been tempted to make a cameo. The man that he shared the ring with was Ace Steel, someone who was CM Punk's very first pro wrestling coach.
Steel caught Punk how to wrestle at the age of 19 and he was just returning the favour. It is great to see the bond that exists between the two men. One never forgets where he came from, despite how far one may go in life, it is often said.
Punk also liked Dave Prazak's post who's one of his best friends from his pro wrestling days. Punk shares great bonds with people that he met long before he made his WWE debut!