I love Bill Corbett’s work on Rifftrax and MST3K, but actually writing jokes for this movie, he is bad. Many of the scripted jokes are your most predictable set ups for lame punchlines. For example, the gruff security officer somehow sees A Chorus Line which makes him gay. Not just gay, but Village People gay with a limp wrist and stereotype voice. You see, because he was so macho you wouldn’t expect that he…*sigh* Where’s the booze?
There is a tendency for works, particularly older works and works aimed at young men, to treat same sex relationships as being inherently funny. Obviously, gay people and gay relationships can be funny for lots of reasons — for example, if the characters are incredibly mismatched, or if the behaviour of one character is amusingly offputting, so this doesn't just apply to any humour derived from gayness or from gay relationships, only when the punchline is that it is gay. Litmus test — if this was heterosexual, would it be (roughly, if not quite) as funny? If not, it's this trope.
Subtropes include Gay Bravado. Begets the humorous parts in Ambiguously Gay, Mistaken for Gay, Ho Yay. Contrast with Have I Mentioned I Am Heterosexual Today?, which could be considered both an Inversion and Subversion.
In Mahou Sensei Negima!, Sakurazaki Setsuna is a bodyguard of sorts who is constantly teased for her overprotective attitude and attraction to her charge, Konoka. It has become a Running Gag for misinterpretations of situations the two get into... and even some correct interpretations.
In Angel Beats! there is a running joke about Otonashi saying something questionable and Hinata asking him if he's gay. And Naoi's...rather extreme admiration of Otonashi after his episode also gets played for laughs a lot.
In Mayo Chiki!, when Kinjiro refuses to be touched by a girl, because he has gynophobia with embarrassing physical symptoms, his male friend loudly questions him if he is gay, much to Kinjiro's embarrassment.
In Death at a Funeral, the main characters' discovery that their father had a dwarf gay lover sparks a plotline revolving around blackmail, but the apparent absurdity of it is also milked for laughter.
In Inception, Eames turning into a woman and flirting with a teammate for comedic effect.
Lamar, one of protagonists in Revenge of the Nerds, is treated as being inherently funny because he's gay; some gags used include his being seen doing aerobics in feminine spandex and leg warmers, and his general disinterest in watching the sorority girls after the group plants cameras in their house. His whole personality revolves solely around his sexual orientation and his race. When the Tri-Lamb commission arrives to the nerds' party and Lewis puts on a record of Old Man River, Lamar was quick to act.
There are several gags revolving around Hollywood, an openly gay character in both Mannequin and its sequel, most of them from his flamboyancy (because, of course, all gay men are very flamboyant in these sorts of movies).
Game of Thrones: Several characters mock King Renly Baratheon and Ser Loras Tyrell due to their homosexuality.
Xena: Warrior Princess, despite all the Ho Yay and general gay subtext in the show, Xena features very little of this. One rare and notable example being from the season four epsiode 'The Play's The Thing' was played for, and recieved, big laughs.
Minya: Gabrielle, I wanted to thank you! I never would have met Pollina if it wasn't for you! In fact, the two of you made me realize something deep down about myself that I guess I always knew, but just didn't dare admit. Yes. I'm a thespian!
Xena: Oh. Hah. Congratulations. You managed to touch someone.
Gabrielle: That's not exactly what I had in mind. I wanted to change violent people into people of peace, not actors. That is what she said, right? Deep down, she's a thespian? Yeah, um, that's what she said. Yeah.
Xena: Why? What'd you think?
Xena being kissed by Miss Artephis (who was actually a transvestite/man in drag) after the latter's victory in the Miss Known World beauty pageant counts as this, but only if you're operating under Trans Equals Gay.
Joxer's triplet brother Jace is the definition of ancient Greek Camp Gay, and only appeared in the second (you guessed it) Musical Episode. Jace's terrible (even by in universe standards) Spanish accent, and incredible Camp stylings would make a young Elton John cringe, and gave a few cheap (and oddly glittery) laughs to the audience of 'Lyre, Lyre Hearts on Fire'.
Buffy the Vampire Slayer, mostly Andrew. The humour there may have revolved more around the closet he was stuck in than anything else, but only if you're reaching for an excuse.
The Season 7 episode "Potential" supplied a particularily wonderful example with the introduction of openly gay potential slayer Kennedy, during a conversation with fellow potential, Rona, about using a wooden stake to fight Vampires.
Rona: I like the feel of wood in my hand.
Kennedy: Lost me there.
These make up the majority of the jokes between Raj and Howard on The Big Bang Theory, more specifically the jokes around them acting like a couple. Also notable in that these jokes are also made about two women, Amy and Penny.
Those are somewhat debatable examples: Raj and Howard are made fun of for how odd their behaviour is for Just Friends, and Amy is made fun of for her obliviousness to how unwelcome her advances are. A far straighter example comes from the occasional joke at the expense of Leonard and Sheldon’s neighbour before Penny, a large, black, cross-dressing man.
Even in season one this trope was fully in effect: among other things, JD pictures the Fat Albert gang doing a "Hi-oh!" after he and Turk exchange Accidental Innuendo about an appendectomy ("I want you inside me"/"Well, I want to be the one inside you") and engage in an extended West Side Story reference in which they take on the roles of Tony and Maria and parody "Tonight".
Barney and Ted also spend an episode wishing they were gay, and then 'adopt' a child together. While played for laughs, its also pretty heartwarming.
Mostly averted with Barney's Straight Gay brother. His sexuality itself isn't really played for laughs, but rather the fact he's black when Barney's white, and the fact he was originally just like Barney if he was attracted to men (and uses the same over-the-top tricks to lure men into bed that Barney uses on women).
There's also the incident during the road trip from hell, where Ted and Marshall had to "cuddle" to conserve warmth in their car during a blizzard. Ruthlessly joked upon by the other 3 members.
A more classical example would be the gay jokes on Torchwood: Miracle Day, especially in the second episode where a flight attendant is badgered about his sexuality until he cracks.
A disproportionate amount of Rex's funny lines involve him making gay jokes about (and generally being rather uncomfortable around) Captain Jack.
Charlie’s fiancée Chelsie’s father, a virulently homophobic man’s man, comes out of the closet, divorces his racist wife, and marries the black man he’s been in love with since he was a young man in the army; subsequent appearances have them behaving like a normal married couple with some amusing banter, and the occasional Right Through the Wall.
Then Evelyn hooked up with the mother of Alan's girlfriend. Cue gay jokes and the children lying about their relationship to their own children, all played for laughs.
Partially averting the Unfortunate Implications, the humour in the first situation derived from the irony of the epitome of Real Men Love Jesus who, according to his wife, is ‘always on the watch for the gay agenda’, come out of the closet, and the aforementioned banter; the awkwardness of having one’s own mother and one’s girlfriend’s dating, causing an off-putting (or, in Alan’s case, possibly arousing) case of Not Blood Siblings; and the general awkwardness of Parental Sexuality Squick in general.
Aside from these cases, the series also features two TranssexualGirl of the Week characters: an old girlfriend of Charlie’s who becomes a new boyfriend of Evelyn’s in season 1, and a transsexual woman Alan dates briefly in season 11. Both of them are the subject of some jokes that fit this trope in a fairly non-offensive way, but their treatment is very positive in general.
Occasionally in House, especially with House and Wilson, and with references to Chase.
The original Monty Python's Flying Circus series did this on a regular basis. Examples include the "Brigadier and Bishop" sketch and Mr. Freight (a.k.a. Great Poof) in "the Visitors" sketch.
Lampshaded in That '70s Show. When Red has a problem with his new neighbors being a gay couple, Kitty points out that he didn't have a problem with The Three Stooges doing it. Red justifies it by saying that it's okay because it was funny.
The George Lopez Show has at least three examples. One is an episode where Ernie lies about being Max's father in order to appeal to women as a single dad and George says some Ho Yay things when he catches him in the act. Another is an episode where George is putting out a newspaper advertisement asking for information about his dad and when Ernie gets done with helping him shorten it, it sounds like an ad asking for a Latino male dating partner. There's also an episode where Carmen is only pretending to be dating a guy named Noah who turns out to be gay. When George finds out, he says to Carmen, "Your boyfriend's in the closet" and this is meant to be funny because her actual boyfriend is also literally in the closet in her bedroom as he's telling her this.
Lots of gay jokes on Friends, especially around Ross' ex wife. Also Chandler's father.
Boy Meets World does this *a lot*. Homosexuality is shown as being weird and hilarious so often, it's hard to wonder if the show would work fifteen years after it aired.
Brits old enough to remember The Dick Emery Show will recall that one of Dicks many faces was a Camp Gay and that really he never got any punchlines, it was just meant to be funny because he was a "poof".
Saturday Night Live can't seem to get through a taping without demonstrating this trope in a sketch, or at the very least in a few Weekend Update jokes.
QI is fond of this trope to the point where you'll be hard pressed to find any episode where there isn't a gay joke made at the expense of (or by) Stephen Fry.
Parodied on Community. Peirce is something of a Troubled Sympathetic Bigot, and he thinks gay jokes are hilarious. Not so much the rest of the group, who call him out on it constantly.
Lana: "Mom wants to know if you're upset about a girl."
Lana: "Dad wants to know if you're upset about a guy."
Clark: "No! No."
Lana: "He has a twisted sense of humor."
Many of the gags involving Kenny James on My Name Is Earl fall into this category.
Causes serious Values Dissonance in Porridge, set in a British prison. One of the minor recurring characters is a gay man put away due to homosexuality still being criminal at that time. While he is treated entirely sympathetically, neither is it treated as an injustice or tragedy that he was put in prison for simply loving someone, and it's jarring to a modern viewer to hear hysterical studio laughter start when he simply mentions his lover. A good example of this is how the final, fully-escalated punchline to a scene of the characters all opening letters from their wives is as simple as the gay prisoner opening his letter.
The old radio comedy show Round The horne, broadcast in a time before homosexuality was fully legalised in Britain, introduced two outrageously out gay characters called Julian and Sandy, played by Hugh Paddick and Kenneth Williams. It could be argued that Julian and Sandy, who were loved for their sheer camp outrageousness, helped pave the way in the middle 1960's for fuller acceptance of homosexuality that led to legal reform later in the decade. They were seen, unltimately, as two sweet inoffensive guys rather than slavering perverted monsters.
It's widely claimed that, in the 1960s, only the more cosmopolitan set would realise exactly what was being implied about Jules and Sandy- to the less sophisticated, it just sounded like a lot of silly voices and nonsense words. (Mind you this is mostly claimed by the 'baby boom' generation, who were children at the time and wouldn't have realised, and their parents may have gone to their graves not admitting that they got those jokes either.) Broadcasting codes at the time were such that you could say what you wanted to if nobody who didn't understand all about it already would realise (the logic would be 'if you understood enough to be offended, you're already as corrupted as us!')
Some of it was "nonsense words", as Julian and Sandy often spoke in Polari, the contemporary gay slang. 
At another point, Tomoya declares as a joke to his class that Kyou is bi and, when she becomes very angry and threatens him to take it back, that she's a lesbian, only for him to freak out when the situation backfires and everyone starts thinking he's gay or bi, too. Weirdly, while in the original Ryou was comically (and thankfully) totally okay with each idea, the anime tries to increase the tension by making her become teary at the thought of her sister being gay, making the scene potentially rather uncomfortable to anyone who's had to deal with homophobia in loved ones in real life.
Mana Khemia has the gag character space prince Muppy whose ending involves him proposing to make Vanye his "queen", which is supposed to be inherantly funny and not a serious ship tease. (Though the other half of the joke is that its Interspecies Romance)
Rewrite has this all over the place. In one early scene, Kotarou speculates jokingly that Yoshino is gay, but then freaks out when he realises that he'd be the only possible love interest. A little later, in an optional mappie scene, a nameless character informs Kotarou that insulting his friend, Yoshino, only makes him more unpopular with the underclassmen, but when Kotarou starts declaring that he loves Yoshino, the guy comments that he'll only get 'weird fans' that way. And then, there's another scene where Kotarou jokes that Yoshino is gay (or beginning 'an interest in Boys Love', anyway), causing Yoshino to punch him and tell him he'll kill him if he says that again. And this is just a few examples...
In Homestuck, Tavros attempts to troll Dave by rapping at him, but his raps keep becoming unintentionally homoerotic, which starts to confuse him and opens him up to some spectacular counter-trolling from Dave, who hits on Tavros insultingly until he gets upset and blocks him.
Generally this is averted, though. Queer characters and relationships are involved which are never milked for cheap laughs, and even in the above case it's later revealed that Tavros belongs to a species where Everyone Is Bi, so his discomfort was entirely based around the unwanted sexual descriptions rather than the gay implications. Notably, Karkat's crush on John, while hilarious, is mostly funny because of how badly Karkat goes about expressing it, and how totally incompatible they are in the way that Karkat wants them to be (specifically, Karkat wants them to have a romance based on mutual hatred, when neither of them hate each other).
Gamzee hitting on Tavros comes partially under this (it's impossible to imagine a heterosexual solicitation resulting in out-of-context Sweet Bro and Hella Jeff references and a Homage Shot to the scene from Problem Sleuth where PS is unable to bring himself to tap a Magic: The Gathering-like card of a man's ass), and partially because it was supposed to amuse the fanbase by canonising a popular but noncanon ship that inspired major Internet Backdraft. Notably, in the next scene dealing with Gamzee's crush on Tavros, it's treated seriously (if disturbingly, and made clear that Gamzee was especially sad about losing Tavros more than anyone else.
The Key Of Awesome's parody of Eminem and Dr. Dre's "I Need A Doctor" is based around mocking the unintentionally homoerotic tone of the video by portraying Eminem as being secretly in love with Dre, who he attempts to make out with while Dre is comatose. This backfires when Dre comes to and freaks out. Things get awkward until Elton John appears to them in a vision and suggests they just make out, join the pride parade and have fun, so they skip off together arm-in-arm.
Hokage: What's with all the gay jokes? You homophobic or something?
Iruka: Geez, Hokage, it's just a joke!
Staple for some writers of Cracked. Though they fully admit the majority of their humor is based on dick jokes (freelance writers are given the title "Purveyor of Dick Jokes"), so it's kind of inevitable that gay insinuations would be included. Gay, lesbian, and bi jokes get full and equal appreciation (they have some choice things to say about Andy Dick, for one thing). But when it comes to actual LGBT people they admire, like Freddy Mercury, they don't joke about it.
This lessened with the addition of Diamanda Hagan, but they still do gay jokes (like Gay Benzaie). The Nostalgia Critic even used Diamanda's lesbianism seriously for a joke in their review of the Heavy Metal movie, asking Diamanda to find out whether a girl would be more willing to sleep with Diamanda if she killed said girl's parents in real life (results: no, she wouldn't).
The The Nostalgia Critic reboot is much worse with than ever before (outright disgusted faces at Frodo/Sam as just one example), and the reason why his LGBT fans complain and point this out is that Doug's previous project, Demo Reel, was full of casual gay with no jokes whatsoever and most people are just confused by the backslide.
In Ménage à 3, Dillon was initially a sort-of-flamboyant Camp Gay, but as time went on, some readers felt that he was flanderized into a walking gay stereotype (although others felt that the seeds of that characterisation were always there). This was lampshaded in his own spin-off comic, Sticky Dilly Buns, where he says he went "from gay, to super ultra mega gay".
He gets just as flustered and embarrassed about Accidental Innuendo involving finding girls attractive so it's pretty even handed and more about that fact that Finn is 13, so this kind of humour is to be expected…
Defied at one point when Brian pointed out these jokes, when targeted at Ryan Seacrest, stopped being funny when he embraced it and started displaying a Gay Bravado.
In American Dad!, their neighbors Greg and Terry encompass this. They are gay; that's the joke. Some various topics are brought up because of this in episodes, such as the two wanting to adopt a child, one telling his father that he is gay, one being a Log Cabin Republican, etc.
The Simpsons does this a lot, especially whenever Smithers is around, but one moment that particularly stands out is the scene in "Homer's Phobia" when Homer takes Bart to visit a steel mill which turns out to be staffed entirely by gays.
Ray Gillette in Archer is mostly fodder for gay jokes.
John Cena would regularly make jokes at the expense of Michael Cole. The punchline to all of them are basically, "ur gay. Hur-hur-hur."
Ten years earlier, Triple H making fun of Kurt Angle the same way, and the entire schtick of Billy and Chuck.
Michael McIntyre tends to play his Camp Straight-ness for these kinds of laughs while making sure the audience knows he's married with kids.
Anytime someone is in a literal closet for any reason, especially when they are planning to come out of it, you can reasonably expect someone to make a joke about it. It's practically joke-bait in and of itself.
"This Guy's In Love With You, Pare (Buddy)" is a song by the Filipino band Parokya ni Edgar (Edgar's Parish). The song is a about a guy discovering his best friend is gay (and is hitting on him); mostly played for laughs. You can listen to the song with English subtitles (and used as a Naruto parody) here.
Louis C.K. mentioned this in one of his stand-up specials; specifically, he grew up around a gay man who acted like a complete stereotype of gay people, and Louis would laugh at him. But, Louis defended himself saying he wasn't laughing because the guy was gay, but because of how "weird and silly" he was acting.