Also doubling as a Brick Joke: in one episode, Garfield & Nermal contend with mutant guppies, who they defeat by chasing them back into the sewer. Said guppies then appear in the subsequent US Acres Quickie; after scaring Wade and Orson, one guppy turns to his fellows and says "Come on guys, let's go see if we can get a guest shot on the Muppet Babies, whaddaya say?" (Muppet Babies aired after the show on CBS at the time).
Aloysius Pig is Kevin Meaney in a pig costume. They both even share two catchphrases! note "That's not right!" and "I don't care!", even though the latter was only said once
In "Clash Of The Titans", as the gang is flying home, Garfield asks if the characters can stop at Teenage Mutant Ninja Turtles so they can get a pizza.
In "Temp Trouble", we have this line: "Mrs. Pig, it's Saturday morning. Do you know where your children are?". Ironically, the thing the quote shouts out to note A message broadcast on TV at 10:00PM was based off Wee Willy Winkie, a nursery rhyme that would be spoofed 8 episodes later.
In "The Discount Of Monte Cristo", Aloysius wants Flipper to rescue him from being stranded on an island.
In "Kiddie Korner", Aloysius says that sitting on a tuffet "sounds naughty". This could be a reference to a Dot's Poetry Corner segment of Animaniacs that aired a year before this episode, where Dot reads Little Mrs. Muffet and uses "tuffet" as a euphemism for "butt", while showing us her panties doing so.
In a weird example of the show having a shout out to itself, one US Acres quickie had Roy on a stage in a competition involving baaing and cocking against Lanolin. One season later, the same stage reappears in the Laryngitis quickie, and he stands on it in almost the exact same manner!
In "Much Ado About Lanolin", the scene where Lanolina trips on her dress is quite similar to the scene in Santa Claus Is Comin' to Town where Burgermeister Meisterburger trips on a duck in exactly the same way. Lanolina, however, did not get her foot in a cast, but yelled at how the stairs were defective.
One rather silly episode has the entire episode purposely having animation errors. At the very end, Garfield leaves and Odie follows, except Odie is Marmaduke
In "Flat Tired", while deciding who to get for the cartoon when Garfield is too tired, the director initially says "Get me Kermit The Frog on the phone," before choosing Odie. Also a bit of an in-joke, since Muppet Babies was also on CBS at the time.
In "Peace and Quiet", Binky refrences the United States Post Office motto, "Neither snow nor rain nor heat nor gloom of night stays these couriers from the swift completion of their appointed rounds", but replaces "couriers" with "clown".