(This page counts for both the comic and the cartoons)
One of the Take That variety occured in the The Simpsons comic book "Clown Therapy", where Krusty states he hangs up Garfield cartoons on his cubicle because he's not allowed to laugh in his workplace.
The opening references that of Garfield and Friends at the beginning, featuring Calvin tap dancing to a CD player (replacing the original's record player) and starting it.
"The Black Turning Funnel, part 1" has a scene with dialogue taken exactly from this strip◊, just between Calvin and his mother.
In "A Calvin and Hobbes Christmas", the line "FIVE BILLION PRESENTS!" (from Calvin's parody of "the 12 Days of Christmas") is from a 12 Days of Christmas feature that appears on the website during Christmas. Also, "Christmas is Here" from A Garfield Christmas is sung near the end.
"So Long, Old Friend" and "Together Again", both from Here Comes Garfield play on the radio in "Tonsil Terror".
Most likely unintentional, but Fat Bastard's lament "I eat because I'm unhappy. I'm unhappy because I eat. it's a vicious cycle" in Austin Powers: The Spy Who Shagged Me is eerily similar to a late eighties Garfield in which he states the same thing, only there it was followed by "That took years to perfect!"
Puss in Boots gives a dry "I hate mondays" after falling in his milk dish in Shrek II.
In Smiley Face, Jane stares at a piece of corn in a frame and decides she'd frame a picture of lasagna because she loves it, and then decides to frame Garfield and eventually James A. Garfield as a subtle way of saying she loves lasagna.
Ted features a scene where the titular character draws on a girl's naked chest to prove Garfield's eyes look like a pair of tits.
In the The Big Bang Theory episode "The Wheaton Reoccurrence", Sheldon gives Amy ice cream for being upset due to studying Cathy. He then states "If you were a cat, I would have bought you a lasagna."
In "The Raiders Minimization", Sheldon is looking for flaws in Amy's favorite newspaper comics to get back at her for pointing out one in Raiders of the Lost Ark. He attempts to find one in Garfield, but finds the comic too funny and gives up. Near the end, he finally finds one: Garfield has no reason to hate Mondays, since he is a cat and has no job.
In the pilot of Crash And Bernstien Crash attempts to send Amanda away in a crate marked "Dubai", a la Garfield attempting to send Nermal to Abu Duabi.
The pilot has Del lamenting eating Cap'n Crunch and watching Garfield on Saturday mornings.
Another episode mentions having a Saturday morning show like Garfield.
One Saturday Night Live episode mentioned the (thankfully) fake "Garfield 3" in an Access Hollywood spoof.
Bloom County had several references, some lighthearted, others not so much. The most notable one is the entire character of Bill the cat, who was introduced by Milo as their way of cashing in on Garfield.
Dogbert showedDilbertGarfield after the latter was accused of "petimony" for petting the neighbor's cat.
The steel lasagna item (don't ask), upon consumption, mentions that the player character feels "somewhat like robo-Garfield".
Likewise, eating a skewered cat appendix gives you a craving for lasagna.
The funny paper hat describes several classic comic strips, one of which being a "schizophrenic loner who can hear his cat's thoughts". (This might be an allusion to Garfield Minus Garfield as well.)
One choice adventure has the Cheshire Cat mentioning his love of lasagna and hatred of Mondays, despite not having a job.
The potion of the field gar. Need I say more?
This potion is made from the squeezings (best not to inquire further) of the mythical field gar. Field gar are recognizable in the wild by their sluggish, obese, orange bodies, and their ravenous appetite for lasagna (a strange evolutionary quirk, since lasagna doesn't naturally occur in their habitat). Biologists who have intensely studied the field gar claim they can hear the gar speaking to them telepathically, but that's probably flashbacks from their wild toad-licking days.
#860 takes screenshots from the quickie of Garfield replacing the phone with a banana from the episode "The Mail Animal/Peanut-Brained Rooster/Mummy Dearest", and recaptions them with the original text as a Recursive AdaptationIn The Style Ofphotonovels.
#1241 edits a strip about ants to have them sing the ant song from "The Picnic Panic".
Sherlock, the blue cross between a helicopter and cow of "Sweet Cuppin Cakes", trying to catch a worm all the time could be referring to the U.S. Acres bits on Garfield and Friends, specifically the pursuit between Booker and the worms.
Robot Chicken referenced it four times. The first has Heathcliff taking him to "Cat Court" for debuting five years later than him, the second features Brecklin Meyer complaining and ending it with "I was in Garfield...", the third (which has Brecklin Meyer as Jon) has Liz announcing Garfield has type two diabetes from too much lasagna which he promptly dies from, causing Jon to get a second one who prefers normal cat food over spaghetti and meatballs and the fourth has Garfield as a contestant on The Fattest Fat Loser.