Smithers' relationship with Burns can be seen in this context. Originally, Smithers' character was supposed to be an exaggeration of the Yes-Man (the sycophantic worker who always sucked up to his boss) and was later his personal servant when Burns was shown more at home than in his office at work, but then came gags like Smithers going to The Maison Derriere just to please his parents — and being disappointed in it — in "Bart After Dark", Smithers cringing and moaning as female strippers gyrate all around him in "A Hunka Hunka Burns in Love," Smithers imagining Mr. Burns jumping out of a cake in only a sash and seductively singing "Happy Birthday, Mr. Smithers" (as seen in "Rosebud"), Smithers having a computerized version of Mr. Burns on his desktop that says, "You're quite good at turning me on" (as seen in "Lisa vs. Malibu Stacy"), Smithers' vacation at an island of men in "Homer the Smithers", and the "flying in through the window" fantasy (as seen in "Marge Gets a Job"), and soon, you have obsessive viewers wondering if Smithers is gay and in the closet or if he has a massive crush on his boss, regardless of gender. Considering that recent episodes have Smithers openly admitting that he's gay (something that was even a plot point in one episode), it's probably the former.
And in episode "Lisa the Skeptic" Smithers kisses Burns on the lips.
Smithers: Oh, what the hell. *smooches Burns*
At one point music teacher Dewey Largo was caught in a car with Smithers (the show's most obviously gay regular), denying wholeheartedly that they were doing anything other than carpooling.
Homer has the occasional mancrush, including many men that have an interest in Marge.
Nelson also seems to be an example of this trope. In "Little Orphan Millie", where Milhouse's parents go missing, Nelson (as well as Bart) are a part of the crowd during school that fawn over Emo Milhouse.
Bart and Milhouse in general. Bart even gives him roses in one episode!
Milhouse's crush on Lisa is partly because she reminds him of Bart. Bart was attracted to Milhouse's cousin, Annika, who looks just like Milhouse but older and female.
When Bart meets an older doppelganger of himself, he notices the man's wife looks just like Milhouse.
They even lampshade it now. In "Postcards from the Wedge", Bart has to get a rectal thermometer check-up from Marge in his bedroom, and Lisa replies "Just close your eyes and think of Milhouse."
In "The Two Mrs. Nahasapeemapetilons" where Apu gets married, Milhouse arbitrarily shows up, and the guys on the commentary track chalk it up to his being Bart's "plus one".
"Mom and Pop Art": When thinking of things to make Homer mad so he can have inspiration for his outsider art, Bart says, "Well, I'm flunking math, and the other day, I was a little attracted to Milhouse!"
Milhouse has also intoxicatedly said about Bart that "this guy here...this is the guy", was very jealous when Bart spent a lot of time with Nelson, and once jumped over a waterfall while exclaiming "I can't live in a world without Bart!".
This quote says it all: "Bart, when I was pushing you away I was really pushing away the thought of being without you." Yes, he (Milhouse) actually did say that. With a rather flirty pose. In response to Bart losing his friend Diggs, who pretty much replaced Milhouse until he was committed.
Diggs (voiced by Daniel Radcliffe) has a few moments of this with Bart, to the point Bart is in tears when he's taken to a mental hospital for trying to fly. The falcon is even mentioned in later episodes with Bart. He could have very well been the Veronica to Milhouse's Betty to Bart's Archie Gay Option if he wasn't a one-shot character.
Homer has also kissed and hugged Ned, filmed him naked in the shower, and Ned puts up with every Jerkass thing Homer does and is generally very kind to Homer.
Ned declares in church that the lord is telling him to confess to something. Cut to Homer watching with fingers crossed (it's usually done for luck) and repeating "Gay...gay...gay...gay...". It's uncertain whether he's hoping Ned is gay so he can have another thing to make fun of him about, or he's hoping Ned is gay because he has implied feelings towards him.
Skinner and Chalmers have had quite a bit of this in recent years. "We'll have to bite from each end! We'll know we're safe when our lips meet in the middle".
Better yet, the thing they're "biting from each end" is a cake shaped like a penis that crashed into Skinner's house while Chalmers was over for dinner.
In "Chief of Hearts", Homer and Chief Wiggum develop a friendship that verges on this at times.
In a similar vein, in "Donnie Fatso", Homer teams up with the FBI to infiltrate the mob, and becomes incredibly close to Fat Tony. True, the constant touching, hugging, and kisses on the cheek could be Hand Waved by Tony being an Italian gentleman, but when Tony dies of a heart attack during a sting, Homer mourns like he's just lost the love of his life. It's rather sweet, and a tad suspect. Tony even lampshades their close bond: "To heterosexual male friendship -the kind the Greeks wrote about."
Homer: This is all your fault, with your non-threatening Bobby Sherman-style good looks! No girl can resist your charm!
Jesse: This was her choice, Mr. Simpson.
Homer: I'm sorry, I wasn't listening, I was lost in your eyes.
In "Double, Double, Boy in Trouble" Bart swaps lives with his rich look-alike and during dinner, Milhouse notices Bart's beautiful "half-siblings". He says they're beautiful, but then says just the girl, he didn't notice the beautiful boy. He says with a dreamy look on his face.
There's "Simpson and Delilah", where Homer meets Karl. Karl helps him work to the top, writes his speeches for him, then tells Homer he isn't a fool. Why not? Because his mother told him never to kiss a fool— which he does then. Homer also accidentally blurts out "I love you Karl- I mean, Marge" when a singing telegram guy shows up at their door.
On one occasion Homer commented on how attractive another man was and that he had been kissed by another man on two separate occasions. While clearly surprised, he didn't react negatively.
Yet another, in "The Haw-Hawed Couple": Bart becomes Nelson's "best friend", and it's played exactly like a relationship, with lines like "I've known him for ages, but we met at a party and hit it off right away" and jealousy over Bart 'flying kites' with another boy. Complete with a Brokeback Mountain homage at the end.
Nelson: Haw! Haw! I touched your heart!
Homer going into fanboy mode over Rainier Wolfcastle in "King of the Hill". "Oh I love your movies and your powersauce bars and your taut... rippling..." Rainier interrupts him before he can finish.
In "Lisa's Date with Density" Nelson's gang seemed to get rather jealous when he began spending a lot of time with Lisa.
Nelson and Jimbo sure seem to have a lot of physical contact whenever they have scenes together. In "Whacking Day" the bullies spend the whole episode locked in a closet together. Nelson and Jimbo hug in comfort over their personal issues.
Sideshow Bob has bonded quite a bit with Snake since he was in prison. They even hug during "Black Widower" and Bob leaves Snake with the words "I'm going to miss you most of all, Snake."
Martin and Nelson have a few moments of their own, with Nelson coming off kind of Tsundere:
Nelson saves Martin from a Shelbyville bully in "Lemon of Troy" when the two are paired up on a mission to rescue Springfield's stolen lemon tree. Martin is overjoyed and Nelson is mostly embarrassed rather than enraged.
In "Grade School Confidential", Nelson's the first person Martin gives an invitation to his birthday party despite Nelson's repeated attempts to brush it off.
In "I'm Spelling as Fast as I Can", they went to space camp together. Martin even held Nelson's hair while he had motion sickness, and when Nelson tells him to shut up he follows up with "commander", sounding embarrassed.
Apu: He used to rob me two, three times a week. Now, Im lucky if I get it once a month. Snake: He never initiates it; I have to do all the work. He just stands there Dr. Swanson: Now now, dont talk through him. Talk to him. Snake: Apu, sometimes when I rob you, its like youre not even there. Apu: That is because you are robbing my brother Sanjay. Snake: Dude, I didnt know. Apu: Just shut up!
Bart and Lisa suspect Sideshow Bob of kidnapping Homer in "Wedding for Disaster". However, it turns out that he's innocent—because the day Homer was kidnapped, Bob was spending the whole day with Krusty. Krusty's alibi dives headfirst into this.
In "Lisa the Drama Queen", Lisa becomes best friends with Juliet Hobbes, a girl with a British accent who likes roleplaying. And in their fantasy world, they're the two queens who rule over the land of Equalia. And then they run away together when Marge, fearing that their friendship is having a bad effect on Lisa, attempts to separate them...
This is based on the plot of Heavenly Creatures, which was in turn based on a true story. The girls WERE budding baby lesbiansnote or at least bisexuals, given their crushes on male celebrities in that incident. And then they killed some people.
There are some amazing Les-Yay undertones between Marge and Belle (the Burlesque house owner) in "Bart After Dark".
In Scenes From The Class Struggle In Springfield, Marge reunites with her old friend from high school, Evelyn Peters, who acts like she's reunited with an old girlfriend who wants to win her back. She seems ESPECIALLY disappointed with hearing that Marge married Homer.
In "The Ned-Liest Catch" Ned finds out Edna has seen a lot of men in the past and ends up seeing them each appear on her face. Patty's face goes back to normal as she says "experiment".
In the same episode, Patty and Selma bought robots programmed to love them. Selma has a male robot, and Patty has a female robot (although that's not too surprising, as Patty already came out as gay in "There's Something About Marrying" (2005 episode)).
Marge and Sarah Wiggum become really close friends in "Uncut Femmes". The episode even ends with them walking down the stares together while locking arms.