EDIT: mystery solved!! it WAS this comic, from march 27th, 1982. the attached image is a FAN EDIT of that comic on the site square root of minus garfield, where it seems like "fench" vs. "fence" may be a very minor in-joke. so i was right all along! now the only question is "why did jim davis use fench in this one instance?" the world may never know. thanks @mintexists for pointing me in the right direction.
EDIT 2: it was just a spelling error and was edited out in later releases.
thinking about a garfield comic i read when i was a kid that used the word "fench" as a synonym for fence. i remember my parents saying it wasn't uncommon but upon a cursory google search it appears this word has no meaning whatsoever.
also upon google searching for "garfield singing on fence comic" i came across the attached comic which i feel like is the one i'm thinking of but it uses fence! but i don't think i made this up because i remember noticing it every single time i read it in the compilation book. i must solve this mystery at some point
