Is it common to use "pope" like this? Is it acceptable to use that word?
The "Pope" is the Bishop of Rome, and thereby the world leader of the Catholic Church. The word "Pope" is not treated as sacred, especially to people who are not Catholic or religious. As long as it is not being used to insult or be offensive, then there is nothing wrong with using the word. I will say though that you won't commonly hear people using "Pope" in jokes just to avoid possibly offending someone.