Orson (adopted mother)
Booker was one of two eggs left behind by their mother. The pig Orson found the eggs and sat on them until they hatched. Being the first thing they saw, Orson obviously had to be the mother. Orson named him Booker, due to his love for book, and as Booker pointed, he was just glad, Orson didn't love kumquats.
Booker spends a lot of time on adventures and chasing worms that somehow always seem to outsmart him.
Garfield and friends
Comics: As egg: May 6, 1986
As Booker: May 22, 1986
Cartoons: Wanted: Wade (September 17, 1988)
Country of origin:
In the cartoons, Booker calls Orson Daddy in stead of Mom (voice by Frank Welker).
Examples (click to enlarge):