Classic Era:
* Detective Comics #140 (1948): The Riddler's first appearance, where he was known as the "Riddle-er".
* Batman #140 (1952): His first appearance as "The Riddler".
* Batman #158 (1964): This issue introduced the iconic green question mark suit design.
Silver Age and Beyond:
* Batman: The Brave and the Bold: Featured the Riddler in several stories.
* Batman: The Animated Series: The Riddler was a recurring villain in this popular series, often depicted as a more sophisticated and intelligent criminal.
* Batman: The Long Halloween: This graphic novel offered a compelling origin story for the Riddler and showcased his intellectual rivalry with the Joker.
* Batman: Hush: This graphic novel explored the Riddler's connection to a larger conspiracy.
* Batman: Year One: The Riddler is featured in this iconic graphic novel.
Modern Era:
* The New 52: The Riddler was redesigned and featured in numerous Batman comics, including "Batman" and "Detective Comics."
* Batman: Arkham Series: The Riddler was a central character in the popular video game series.
* Batman: Rebirth: The Riddler continues to appear in the current ongoing Batman series and other related titles.
Other Comics:
* Justice League: The Riddler has occasionally been featured in Justice League stories.
* Teen Titans: The Riddler has occasionally appeared in Teen Titans stories.
* The Batman Adventures: He was a featured villain in this popular comic series inspired by the "Batman: The Animated Series."
Beyond Batman Comics:
* The Riddler #1 (1970): The Riddler got his own limited series.
* Batman: The Riddler (2007): A one-shot graphic novel focusing on the Riddler's origin.
* The Riddler (2022): A one-shot graphic novel featuring a modern take on the character.
This is just a sampling of the Riddler's appearances in comics. He's a popular character and has been featured in countless stories throughout the years.