If The Acts of Peter are to be believed, Peter was like that kid who would eat hot sauce laced with dirt if you just dared him hard enough. He'd do anything to convince unbelievers he was a true representative of God, which kind of makes sense if you remember that Peter was the guy who denied even knowing Jesus three times the night before the Crucifixion. He had a lot of making up to do.
"We don't even have a number for how many Hail Marys that is. Just keep praying till I tell you to stop."
Now, we're going to go more into this in a minute, but Peter had a bizarre grudge against a Jewish magician named Simon. Simon, according to Peter, was leading people astray and sullying God's name. In Peter's head, the whole Simon thing could be solved with a few miracles. Miracle One: Give a dog the voice of a man to send a warning.
And Peter, seeing a great dog bound with a strong chain, went to him and loosed him, and when he was loosed the dog received a man's voice and said unto Peter: What dost thou bid me to do, thou servant of the unspeakable and living God? Peter said unto him: Go in and say unto Simon in the midst of his company: Peter saith unto thee, Come forth abroad, for thy sake am I come to Rome, thou wicked one and deceiver of simple souls.