From Wikipedia, a list of baseball mascots, present & historical.
I did not know that in the absense of the Chicken, San Diego has the Swinging Friar, a person dressed as a friar swinging a baseball bat.
Did you know: The first "costumed/character" in pro sports was Mr. Met, from the New York Mets. It was also his "birthday" yesterday, on April 11. His official debut was on April 14, 1964.