In many current comic books, the origin issue comes in their own title comic book. In the past though, many characters were spotlighted in comic books that were more of a smorgasbord of content. Some comic books had more than one character in it and new characters were introduced all the time. Spider-Man’s origin story came about in Amazing Fantasy #15 and was supposed to be the last issue. Stan Lee was given the go ahead to premiere his latest character by himself and illustrator Steve Ditko, Spider-Man.
For some character though, the origin issue might not come for some time. In the case of Wolverine, part of the characters charm was that his past was unknown to the rest of the world. His past remained a mystery for decades until it was finally revealed to the world in a special limited series called Wolverine: Origins. It showcased Wolverine as a young man and chronicled not only his start on the path to becoming Wolverine, but the start of his long running feud with Sabertooth.
Sometimes writers will go back and change parts of the origin story as was the case with DC’s comics Golden and Silver Age characters. For a time, the two groups were considered to be part of two separate realities with two Superman’s and two Green Lanterns. This was all changed when the two universes were merged and parts of both origins were worked into the characters.
For collectors, the origin issue is a prized possession. It is the start of what made that character and turned them into the hero or villain they are today. Without the origin issue, fans would have way to many questions and would not be able to sink their teeth into what makes the character great.