The phrase "initial appearance" refers to the first time someone is seen or noticed. It is the first time they make their presence known or show up in a certain situation. Full definition
A store clerk once had a favorite customer who was much larger than initial appearances showed. (professorshouse.com)
The season pass, which has six parts will offer downloadable content based on The Dark Knight, Man of Steel, and the 75th anniversary of Batman's initial appearance in Detective Comics. (the-games-blog.com)