Doctor 13: Architecture & Mortality is a metatextual comic by Brian Azzarello and Cliff Chiang, about superhero universe retcons and the lives that get snuffed out when they happen. All of the main characters in the story are long-forgotten 8th-string DC characters fighting The Architects, who are comics creators. There are lots of puns and things that must have been awesomely fun to draw because they’re pretty excellent to look at (in the same way Dr. McNinja does this kind of madness). By the end the Nazi Gorilla Vampire is saying “I guess I’m an anti-hero” and the fourth wall is smashed quite nicely. But there’s also a good little meditation on how the past is all the universe there really is.
I was actually surprised this was done back in 2007. It felt very much like a pre-New 52 kind of story, but I guess that just shows how regurgitative the business of superhero comics really is.