The Griddler is a McDonaldland character that was seemingly used in commercials from 2003-2006 before seemingly disappearing without a trace, becoming an urban legend among McDonald's historians. According to some sources, the Griddler was similar in appearance to Mayor McCheese and Officer Big Mac, having a giant McGriddle for a head, and would steal other peoples' McGriddles for himself, similar to the Hamburglar.
Instagram post mentioning the Griddler
While there are no pictures of the Griddler himself on the internet, he has been mentioned in a post from the official Ronald McDonald instagram account, confirming his existence while not providing visual evidence of his appearance.