Large Marge is a name of a Series 3 Garbage Pail Kid.
Krusty as the guest villain "Clownface" in the classic Batman series could be an oblique reference to Maurice Evan's turn as The Puzzler, a one-shot villain created for the episode "The Puzzles are Coming!/The Duo is Slumming". Frank Gorshin, who played The Riddler, was either unavailable due to a prior commitment or holding out due to a contract dispute (depending on which version of the tale one reads), so a Riddler script was hastily rewritten to suit Puzzler. Krusty's resemblance to The Joker suggests that, in the Simpsons universe, Cesar Romero got the same deal.
Former U.S. Presidents Jimmy Carter, Bill Clinton, and George H. W. Bush (who parody The Three Stooges).
Near the beginning, Marge is driving with Maggie in the car and turns the station to Radio Disney, which plays music for babies. The song playing is "Who Left the Milk Out?" which Marge loves, but Maggie can't stand.
Over the closing credits, the song playing is "Who Let Her Jugs Out? ", referring to Marge's flashing her breasts to the crowd near the end of the episode. The lyrics include Homer saying "D'oh!" several times.
Comic Book Guy compares Marge to "X-Men #3 in a Mylar bag", which he would see as something rare and extremely valuable. The real X-Men #3 comic came out in early 1964, and Mylar bags are commonly used to protect comic books from deterioration and preserve their value.
The Sea Captain says Marge is like Jacqueline Bisset in his "fav'rite film, The Deep". The film's opening scene (which has achieved iconic status) shows Bisset swimming underwater wearing only a thin white T-shirt and bikini bottoms, putting her figure on impressive display.
This is the last episode to feature Jan Hooks as Manjula.
"El Homo", Homer's attempted graffiti alias, is obviously based on Bart's far more successful alias, "El Barto".
Some scenes involving Marge's enhanced breasts were shown in FOX promos/commercials, but not in the episode (possibly edited due to censorship):
Marge hides her breasts in the sink.
Marge uses pans to cover up her breasts when Bart comes into the kitchen.
Marge tries to cover her breasts with tennis rackets.
Bart and Lisa run into Homer's and Marge's bedroom at night. Marge is in her robe and Bart stares at her cleavage. Marge frantically points to her face and tells Bart to "Just focus on Mommy's face", to which Bart replies, "I'm trying, Mom."
One of the "before and after" pictures at the plastic surgery clinic shows Moe as his regular self and after having had plastic surgery (in "Pygmoelian").
Even though Sideshow Bob appears in the promo card among the men entranced by Marge (who is implied in the image to have exposed her breasts in public), he is never seen in the episode itself.
Similarly, yet another hint at Waylon Smithers, Jr.'s homosexuality was shown in the promo card. Of the male characters who were shown to be shocked at Marge's implied indecent exposure in the card, only Smithers was shown covering his eyes in horror and disgust.
When Bart is in his Krusty the Clown sleeping bag, at one point Krusty's face is yellow when it's supposed to be white. Also he has a comb over just like Homer. Maybe Bart got during Homer's time has Krusty, in Homie the Clown.
The sound mysteriously pauses when Krusty rushes out of the crowd to save Milhouse at the Springfield Shoe expo trade show.
During the shoe expo, Marge's dress has conventional over-the-shoulder straps for most of the time. But when she flashes her breasts to the crowd, her dress changes to a halter top (rather than sliding the straps off of her shoulders, she unfastens the dress at the back of her neck).