Turtles on The Simpsons

The Simpsons have a lot of turtle references. It seems unusually high for a non-recurring 'character'. (I've counted two per season on average.) So far I haven't detected a pattern to when the references occur, but I have my suspicions.

Episode list

Ep #	Episode Title	Reference
04x08	New Kid on the Block	Decor in the Frying Dutchman includes a turtle in a net
05x17	Bart Gets an Elephant	The Turtle Wax turtle grabs Homer's hair
06x07	Bart's Girlfriend	After Bart's new girlfriend pulls a fire alarm, Willy attempts to save the wee tur'les. Willy: If I don't save the wee tur'les, who will? [beat] doh! Save me from the wee tur'les, they were too quick for me aaaggghh...
06x08	Lisa On Ice	When Bart's team wins a hockey game, Homer pulls out a turtle Homer: Well Boy, you won, so I'm going to live up to my side of the agreement. Here's your turtle, alive and well. Meanwhile, Lisa finds she's failing gym class and imagines being impeached from the presidency in the future because she failed gym Justice: I sentence you to a lifetime of horror on Monster Island. [aside] Don't worry, it's just a name. Lisa: [running from Gamera] He said it was just a name! Fellow runner: What he meant was that Monster Island is actually a peninsula.
06x20	Two Dozen and One Greyhounds	Mr. Burns: Some men hunt for sport, others hunt for food. The only thing I'm hunting for, is an outfit that looks good... See... my... Vest. See my vest. Made from real gorilla chest. See this sweater, there's no better, than authentic Irish Setter. See this hat? 'Twas my cat, My evening wear vampire bat. These white slippers are albino African endangered rhino. Grizzly bear underwear, Turtle's necks I've got my share. Beret of Poodle on my noodle I shall rest. Try my red robin suit, it comes one breast or two. See my vest. See my vest. See my vest. Like my loafers? Former gophers, It was that or skin my chauffeurs but a greyhound fur tuxedo would be best. So let's prepare these dogs... Maid: Kill two for matching clogs. Mr. Burns: See my vest, see my vest, oh please won't you see... my... Vest! I really like the vest. Smithers: I gathered, yeah... Lisa: He's gonna make a tuxedo out of our puppies! Bart: [still humming the tune] Na na na na na na naa naaaa... Lisa: Bart! Bart: Sorry... You gotta admit it's catchy.
08x09	El Viaje Misterioso de Nuestro Homer	Homer goes on a vision quest after eating the Merciless Peppers of Quetzalsacatanango. Homer: Huh? A tortoise?! [reading] Follow... the... [gasp] This must be why I'm here! Follow the what!? Follow the what!? Hurry up! [beat] D'Oh!
08x10	The Springfield Files	Mulder and Scully, while investigating Homer's claim of an alien sighting, run across Abe who's lost his teeth to a turtle. Abe: For the love of God help me! I've been here for four days and a turtle's got ahold of my teeth! There he is! [high speed chase] [...] Ow! He bit me with my own teeth!
09x17	Lisa the Simpson	Lisa reviews Yertle the Turtle, possibly the best book ever written on the subject of turtle stacking.
10x05	When You Dish Upon a Star	Snapping turtles chase after Homer
10x23	Thirty Minutes Over Tokyo	Returning from a trip to Tokyo, the plane the Simpsons are on is shaken. Pilot: Uh, folks, we're experiencing some moderate Godzilla-related turbulence at this time, so I'm going to go ahead and ask you to put your seatbelts back on. When we get to 35 thousand feet, he usually does let go, so from there on out, all we have to worry about is Mothra, and, uh, we do have reports he's tied up with Gamera and Rodan at the present time. Thank you very much.
11x03	Guess Who's Coming to Criticize Dinner	Another appearance of the turtle decor from the Frying Dutchman
11x15	Missionary Impossible	Homer wears a turtle-shell helmet in a nod to The Flinstones
11x19	Kill the Alligator and Run	After hitting an alligator, Homer dives in the swamp to flee the police and comes up with a few animals biting him, including a little turtle.
12x09	HOMЯ	Homer has a crayon removed from his brain, improving his intelligence. In a visit to the library we run across Cletus about to make some turtle soup. Lisa: I think books have an amazing power to bring people together. Look, even Cletus is checking one out. [Cletus pulls out a turtle and a bib] Cletus: Now hold still. Nothing cracks a turtle like Leon Uris. [turtle bites him] Cletus: Ow! Dangit! [drops book on his finger] Cletus: Ow!
14x03	Bart vs. Lisa vs. The Third Grade	Bart is demoted to the third grade and Lisa is promoted to the third grade. In the background we see that the third grade classroom has a pet turtle.
14x04	Large Marge	While Lisa and Homer spend their father-daughter time building a house for Domiciles for the Destitute, Homer paints "El Homo" on the house trying to be cool like "El Barto". Then after realizing how it sounds he desperately paints over it. Lisa: Dad, you're getting paint on your wedding ring! Homer: Huh? Oh right. Can you hold it? Lisa: This is a Band-Aid wrapped in tin foil. Homer: My real ring's inside a turtle. Marge thinks she sees Homer flirting and goes to a plastic surgeon to get liposuction, but ends up getting breast implants. Hilarity ensues.
14x06	The Great Louse Detective	Marge goes to a spa and gets a Turtle Massage after which, the turtles are tossed into a bin marked "used turtles."
14x07	Special Edna	"And now, enjoy the soothing music of The Turtles" (OK, so this reference is cheating since it's referring to the band, not to turtles themselves, but I'm counting it :P)
14x20	Brake My Wife, Please	A turtle attacks Bart
14x21	The Bart of War	While cleaning up litter, Kirk Van Houten (leading the Cavalry Kids) accidentally impales a tortoise.
15x12	Milhouse Doesn't Live Here Anymore	Milhouse and his mother move to Capital City, leaving Bart to adopt Lisa as his new best friend. Lisa: The mound builders worshiped turtles as well as badgers, snakes, and other animals. Bart: Thank god we've come to our senses and worship a carpenter who lived 2000 years ago.
15x16	The Wandering Juvie	Bart gets sent to juvenile hall. Yard equipment includes a rocking turtle.
16x14	The Seven-Beer Snitch	In order to find out why Snowball likes another family better than the Simpsons, Bart comes up with an excuse to see in their house. Bart: My baby turtle crawled into your basement window! Woman: Oh, you poor boy. What's your turtle's name? Bart: [looking at woman] Uhh... Apronboobsface? Woman: Really? Well, let's go find him!.
16x15	Future-Drama	Bart and Lisa find themselves in Prof. Frink's basement and he uses the science of astrology on his new computer to show them their future, eight years from next Tuesday. At their graduation party, Nelson flees fatherhood on the back of a sea turtle.
16x16	Don't Fear The Roofer	Homer goes in for electroshock therapy because everyone believes he's crazy. Bart asks him to hold his dead turtle while he's getting shocked to try to revive it.
16x17	The Heartbroke Kid	(Unconfirmed. Need to get a screenshot.) Bart was watching itchy and scratchy. and there was an explosion in itchy and scratchy. for a brief second you could see a DEAD TURTLE hurled across the screen.
17x18	The Wettest Stories Ever Told	In Mutiny on the Barty (a parody of Mutiny on the Bounty), Skinner gets marooned with Willy, who then maroons him on a turtle. (Seymour) Bligh: Sing a round! Willie: Row row row your boat, gently down the stream, Merrily, Merrily, row row, oh so merrily, not so merrily, row row, very merrily... [gives up] I can't do it, sir! I'm just one man! Bligh: What are you gonna do? Mutiny? [cuts to Bligh on a sea turtle as Willie rows away] Bligh: Swim faster or I'll have you made into soup! What are you gonna do? Go underwater? [the sea turtle does so] Bligh: [underwater] You call this "deep"?!
17x19	Girls Just Want to Have Sums	At the beginning of the episode, the Simpsons are attending Stab-a-Lot: the Itchy and Scratchy Musical (a parody on The Lion King / Spamalot), and an actor in a turtle costume leads the animals down the aisle.
18x04	Treehouse of Horror XVII	In the You Gotta Know When To Golem segment, Homer mentions Bart's turtle. *loud moan* Homer: [drunk] Bart, there's something I have to tell you, father to son. I passed out on your turtle and killed it. Someday you'll thank me.
18x10	The Wife Aquatic	Marge goes back to a happy place from her childhood, only to find it's not what she remembered. A carousel she loved has a turtle on it.
18x12	Little Big Girl	Indian reporter: In the name of the Great Turtle, will you just answer the question!?
18x15	Rome-old and Juli-eh	Marge: Awwww look at Grandpa and Selma frolicking in the water. Homer: It's not right! It's like an old sea turtle dating a suitcase that fell out of a plane. (audio) (Loved the parody of the Battle of Helm's Deep in this episode.)
	Unknown	I've seen some turtle references in chalkboard gags There's a quote on the 'net that has Kent Brockman saying "I guess you can call him the little turtle who couldn't! Check our website for recipes." I have a Simpsons figure of Maggie on the back of a turtle

Current count: 32 known episodes plus about 3 or 4 references from unknown episodes