The Ren & Stimpy Show

The Ren & Stimpy Show was an American animated TV series, created by John Kricfalusi between 1991 and 1996, starring an aggressive chihuahua named Ren and a dim-witted cat named Stimpy having surreal cartoony adventures.

References to Ren and Stimpy on Simpsons albums
On the cover of The Yellow Album (1998) a Krusty doll can be seen with the text The Simpsons salute "Ren and Stimpy", in parody of the doll on The Beatles' Sgt. Peppers album which salutes The Rolling Stones.