Rack & Can
Wikisimpsons - The Simpsons Wiki
Rack & Can is a pornographic magazine that Krusty reads.
The magazine is one of many that can be found on "Krusty's Magazine Rack!"
 Behind the Laughter
The magazine's target audience is evidently breast and buttocks enthusiasts, as "rack" and "can" are (respectively) slang term for those body parts.