Were this to happen during the more villainous runs of CM Punk's timeline, it wouldn't have been quite so weird. Instead, this fleeting lapse of character occurred in Punk's last ever WWE match, the 2014 Royal Rumble. In this booking, he was at his wits end, both physically and mentally.
Character-wise, he was babyface to the max and locked in a supposedly long- term battle with Triple H's Authority. So when the 4 ft 5 El Torito entered the Rumble with his white bull costume fully donned, and engaged in a showdown with Punk, it was surprising to see the Voice of the Voiceless have a laugh at the expense of the legendary luchador.
Whilst playing the old 'holding the short guy at arm's length' gag, Punk laughed mockingly in favour of a fan pop. It was only seconds before Punk's juvenile jest backfired and he ended up flat on the ground, which by all accounts he deserved. Though fun and harmless in the long run, it wasn't very characteristic on CM Punk's part.
As all records show, he was past caring at this point.