SpongeBob is not on the official gay cartoon list. Perhaps he is just bisexual.
For peoples edification here is the official gay toon list
Tinky Winky
Admittedly not actually a cartoon but close enough. Tinky is one of the fleece aliens from the British childrens series Teletubbies," Tinky was outed by avid gay fanatic Jerry Fallwell
Falwell cited the following evidence as to Tinkys sexual orientation: He's purple, the gay color; he has an antenna shaped like a triangle, the gay symbol; and he carries a purse, something all gay people do.
Fred Flintstone
Evidence: Wears an orange dress with little triangles on it (triangles rememeber are the gay symbol). Hangs out with his dumpy pal Barney far more than he does with his sexy wife Wilma. The show's theme song ends "...we'll have a gay old time!" His nickname on the Bedrock bowling team: "Twinkle-toes."
Bugs Bunny
Evidence: Often stands with hand on hip. Plays a hairdresser in one episode. Loves opera. Bugs has more dresses than J. Edgar Hoover at Mardi Gras. Loves to throw on a top hat and tails and belt out Broadway show-tunes with his buddy Daffy -- who, it's worth noting, has a lisp.
Velma Dinkley (of Scooby Doo fame)
Evidence: Always tries to sit next to Daphne in the Mystery Machine. Sports that butch haircut. Has broad shoulders and accentuates this by wearing thick turtleneck-sweaters and knee socks. Never once shagged Shaggy. The biggest clue though is Velmas enjoyment of sensible shoes.
Batman and Robin
Evidence: Robin's nickname: Boy Wonder. Batman's real name: Bruce. Both wear tights. They're in great shape. They like to show each other their "grappling hooks."
Peppermint Patty
Evidence: Has a deep, gravelly voice. Wears pants, not dresses like the other Peanuts gals. Plays a mean game of football. Always hanging out with that androgynous Marcie (who refers to Patty as Sir possibly indicating the two have a S&M relationship) Wears comfortable shoes.
The Pink Panther
Evidence: the walk, the cigarette holder
and the fact he is PINK!
Waylon Smithers The closeted sidekick to Mr Burns in the Simpsons.
Evidence: Theres more to his loyalty to Burns than first meets the eye. Simpsons nerds will recall at least twenty episodes when Smithers declares his love, like the one where it appears that the world is coming to an end, Smithers says "Oh, what the hell," and kisses Mr. Burns full on the lips.
Yogi Bear and Boo-Boo
Evidence: Yogi was always well dressed (for a cartoon bear) and his roommate Boo Boo kept a pretty tidy cave. Yogi had a fascination for "lovely picnic baskets" and he was a connoisseur of food. He also liked to taunt & flirt with Ranger Smith and that seemed to really bother Boo Boo. Despite the advances of Cindi Bear Yogi still chose to hibrinate in the same bed with BooBoo.
Hefty Smurf. Most people assume Vanity Smurf was the homosexual of the program but he was just overly narcissistic
in reality it was the overcompensating Hefty Smurf that was a homosexual.
Bert and Ernie
Again not actually a cartoon
but close. Evidence: nipple rings
dont ask how I know Bert has them
Popeye
Evidence: Eats lots of salad. Wears a sailor suit, even though he hasn't been on a ship in years. Does little sailor-dances. Dates a flat-chested transvestite named Olive Oyl. Best friend named Wimpy. Had A LOT of physical contact with the bearish Bluto. Strong advocate of the don't ask, don't tell policy.
Snagglepuss
Evidence: Snagglepuss began his career as a sheep-stealing mountain lion in Quick Draw McGraw cartoons, I shall not even begin to speculate just what he did with those sheep. He also appeared in cartoons with Augie Dogg and Doggie Daddy, rumored to have been a wealthy older dog and his "cabana boy," as it were. Snagglepuss' "exit, stage left" catchphrase clearly put him in the camp of theater-folk.
Dr. Benton Quest - Johnny Quests Dad
Evidence: Always well groomed even in the deepest jungle. Always shared a tent with Roger "Race" Bannon. Benton and Race were early advocates of gay adoption.
The Care Bears
Evidence: part of the radical fairy movement. Lived in commune on clouds and did nothing but talk about happiness and sharing and friendship. Of special note Cheer Bear has the gay pride flag tattooed onto his chest.
Ace and Gary. the Ambiguously Gay Duo
Not that ambiguous at all.
He-Man
Evidence: No heterosexual man looks like that.
Tennessee Tuxedo and Chumley the Walrus
Evidence: well
do you REALLY need any?