On a 1999 live broadcast of WCW Nitro, pro wrestler Sid Viscious was shown backstage talking on the big screen to Kevin Nash who was in the ring. He said "I'm twice the man you are, and have half the brain you do," Kevin Nash fell to his knees and laughed uncontrollably for the next minute or so.
Yeah, they do have a "script" that they pretty much follow when talking. But there are times that they may 'slip-up' in what they say. This may have been one of those times.
Not a all wrestlers have a script, the more talented ones are told what they need to get across when talking and then the wrestler goes out a figures out what he is going to say on the spot