Quite possibly one of Jim Davis' earliest strips
At least that's what they claim in Stripper's Guide, the highly recommended blog by Allan Holtz, collector and historian of comics and newspaper strips, and author of "American Newspaper Comics: An Encyclopedic Reference Guide".
Garfield's predecessors
A Garfield lover, on his YouTube channel called"Quinton Reviews", has discovered some of Jim Davis' early work. Quinton found the strip"Gnorm Gnat", in which different insects appear as characters, and which some believed for a while to be a myth invented by Davis himself as filler in interviews, although there were many references to them.
Gnorman and Lyman in a Gnorm Gnat strip from January 1975
But this is just a foretaste of another major discovery, the original Garfield weekly strip, then titled"Jon", in which the famous lasagna-loving cat was born in a small local weekly newspaper two years before the strip became world-famous through syndication.
Garfield has a new birthday
This discovery disproves and completely changes the story of Garfield's birth, which, even on his official website, dated the first Garfield strip as being published on 19 June 1978. He had been born two years earlier, his first appearance was on 8 January 1976
The first Garfiel strip published on 8 January 1976 in The Pendleton Times, introducing the characters.
Davis, for reasons unknown, has kept these strips "hidden" for the last forty years. Quinton Reviews explains all this and some other curious things in their video entitled"Finding Lost Garfield Comics".
In the video, he also adds a 47-page PDF compiling some of the "Gnorm Gnat" and "Jon" strips published in The Pendleton Times between 1975 and 1978, where I found the strips illustrating this post.