More or less the entire male cast of Merlin seems to go there from time to time, but the frankly incredible levels of Ho Yay between Arthur and Merlin (I defy anyone not to have contemplated a manservant gag at least once) has become one of the main dynamics upon which the show is built, to the extent where they have actually become a Fan-Preferred Couple. (It should be noted that Arthur and Merlin are both the same age in this version, making it rather less creepy).
Oh yes. Even the Great Dragon ships these two. "A half cannot truly hate that which makes it whole," much?
How about these lines, which may be a case of Getting Crap Past the Radar or just Accidental Innuendo. Given the fact that almost the entire Merlin fandom ships Merlin/Arthur and that the whole cast knows about that, the former choice is the most probable one.
Merlin: You've not had your breakfast this morning, have you?
Arthur: I'll have you for breakfast!
Then there's this scene where Merlin says he's too tired from riding the horse all day and Arthur immediately replies with "Is your little bottom sore?".
In season 2, Merlin steals a dress from Morgana and everyone who sees him with the dress immediately jumps to various conclusions regarding his sexuality. When Arthur passes near him he looks confused and intrigued, and later he even tells him the colour of the dress suits him, implying that he has mentally pictured Merlin in a dress.
Don't forget the many emotional scenes between them and the fact that they grow attached to each other really fast in spite of the fact that they hate each other in the first episode.
Also, in the very first reunion of the cast, after the filming of the first episodes, some people from the cast discuss about this subject and joke about it, telling Bradley and Colin that they could actually be gay icons. One of them hilariously compares it to something else:
In The Last Dragonlord, Merlin gets worried when Arthur has to go face the dragon, to the point where he says: "I know it's hard for you to understand how I feel...", to which Arthur pulls off a face that implies he actually thinks Merlin refers to that kind of feelings.
Some argue that the palpable Ho Yay between Colin Morgan and Bradley James is one of the main reasons this chemistry comes across so strongly.
Their co-stars, Katie Mcgrath (Morgana), and Angel Coulby (Gwen) even ships them as she watches a scene of the boys in one of the DVD commentaries and, when Arthur says 'Merlin...' in the scene, she jokes and continues his line with 'I love you', revealing the fact she wants Arthur to declare his love for Merlin.
Katie: ‘I love you.’
Colin: Come on, you’re just fueling stuff here for websites, to be serious.
Katie: Okay, I’ll stop.
Angel: We don’t need to fuel it, it’s already there.
Katie: laughing Exactly!
Also, when she's asked in an interview what does she think of the fans pulling a romance between Arthur and Merlin, she says it's genius and everyone who thinks that should totally go for the idea.
Bradley is also the BIGGEST Colin fanboy. From their videos, Bradley seems to harbour quite an affection for Colin as he films Colin the most from all his co-stars, likes to taunt him and act like a show-off in front of him and he also reveals that he is always reluctant when he has to be violent to him and act like a bully in their scenes because he believes Colin is tiny and fragile. He even declares that Colin is his favorite co-star and that a little piece of his heart goes to him.
Bradley: Your cheekbones are kicking right off in this shot, mate.
Colin: Are they?
Bradley: Oh yeah.
Colin: You likin' them?
When he is told by the interviewer that Merlin and Arthur are obviously going to grow old together, Bradley replies with this:
Bradley: Do you mean Merlin and Arthur are going to grow old together, or Colin and Bradley?
In the same vein, from one of the season 1 video diaries, after explaining that the Bradley-Colin relationship has taken time to develop because Colin is very reserved:
Bradley: But as time has gone on, I've suddenly learned about all these endearing qualities that he has. Everyone else was talking about "Oh, we love Colin! Oh, Colin is so great!" Alright, yeah, whatever. Um, but it turns out, he is pretty special.
Season four lays it on thicker than any other previous season, and it's a wonder it hasn't been declared Canon yet.
4x02 includes the wonderful Ho Yay bonus of Merlin and Lancelot talking about what it takes to give your life for somebody else's, in reference to Merlin's plan of giving up his life to close the veil so Arthur won't have to. Merlin's line is 'Something more important than anything'. Your feelings for Arthur are showing, Merlin.
The same episode gives us the scene where Merlin shows up alive and well and knights greet him with hugs. Arthur, on the other hand, gives him a silent, happy look which is quite loving.
4x03 is chock full of Ho Yay of the highest quality. Merlin doesn't act towards Arthur as a symphathetic friend; he acts like his boyfriend, and I'm not kidding. During Arthur's coronation Merlin is practically glowing with pride and love.
He isn't going to ... yes, ladies and gentlemen, he is. Merlin just grabbed Arthur's ass.
4x06 brings us the first Arthur/Merlin hug. In fact, the entire episode is a decent slash fanfiction.
The same episode also gives us Arthur carrying an injured Merlin on his back, Arthur calling Merlin "brave" and a "good servant", Merlin facing what seems like a certain death in order to protect Arthur, Arthur rejecting a capable servant in favour of getting Merlin back, Arthur and Gwaine looking for Merlin despite the fact it seems pretty much hopeless at this point, brainwashed!Merlin acting jealous and bitching over Gwen, Arthur casually walking around naked when he thinks he is alone with Merlin and so on, and so on. Subtlety is overrated anyway.
In the same episode Arthur tells us Merlin is the only one he can trust. Not Gwen, not Agravaine, not his knights, but Merlin. Sadly, Merlin is brainwashed at the time and probably doesn't remember it at all.
He gets a new servant and is fully dissatisfied with his service because, while Merlin is always late, not very good at his job, seems to spend most of his time at the tavern, and has the smallest bladder ever - Merlin is his manservant, "And I rather like it that way".
At the end of 4x10 Merlin asks for a hug; Arthur stops dead in his tracks and then promptly tackles him. Combined with the glorious hug from 4x06, this is a considerable change in Arthur's attitude to Merlin.
In 4x11, when Princess Mithian comes, it looks very much like Merlin has been crying, what with how red his eyes are. Although you're supposed to think that he was sad that Arthur was betraying Gwen, it looked a lot like he was the one being betrayed. Same with when Arthur announced the marriage, and Merlin ran after him when the court was dismissed— much like a lover discovering he was the other man all along.
4x12: Merlin spends half of the episode bossing Arthur around. Arthur is enchanted at the time, but Dom/sub vibes are still there. And Merlin definitely enjoys it a bit too much.
Add the first scene of this episode, which features Merlin standing in front of a table, Arthur approaching him — with no pants — then grabbing Merlin's shoulders and turning him around... Talk about getting something past the radar...
Season 4 finale has some very bromance-y Merthur moments, and not the usual banter. When Merlin goes missing at one point, Arthur immediately turns around to search for him without thinking twice. And then we get this gem from him:
Arthur: I came back because you are the only friend I have and I can't bear to lose you.
The bromance so prevalent it seems taken almost completely for granted these days: 5x01 was filled with so much Merlin/Arthur hoyay that it would have been a cause of much comment had it appeared in any other series, but it's just par for the course for Merlin - it's been over a week since the episode was broadcast and this is the first comment on it. Exhibit A: Merlin and Arthur spending a whole night tangled up together in a net when it would have been a second's work for Merlin to release them is baffling, unless you consider that Merlin was perhaps enjoying it too much to want to be let loose. Not to mention that it apparently took several hours for Arthur to realise that he could just try getting his sword out.
Arthur dies in Merlin's arms. Even in the last freaking episode, they threw something in there for the slash fans.
The entire final episode is one long shipfest for slash fans to pick apart.
So many intense conversations often with the love theme playing over the top of them made it look like Merlin and Arthur were finally going to kiss.
Arthur specifically requests that Merlin holds him as he dies. Their final conversation is heartwrenching, and both characters seem like they're about to spit out "I love you!" at any second.
Merlin's utterly distraught expression as he pushes the boat holding Arthur's body off the shore of the lake towards the Isle of Avalon.
Arthur comes to terms with Merlin's magic and accepts him for it, which is arguably part of the point of the whole series.
Merlin remains dedicated to Arthur even when he's being a dick to him after The Reveal.
Their faces are very close in almost every single conversation they have. And they're shot like lovers.
Arthur getting up from bed with Gwen after having had a dream sent by Merlin warning him of Mordred's attack looks suspiciously like he had a certain kind of dream about Merlin...
"Just...just hold me...please." Doubles as Tear Jerker.
The Les Yay between Morgana and Gwen is pretty noticable as well. Go on, go through the episodes and take a shot every time they share a lingering glance or gratuitious contact. Bet you won't make it through half a season before dying of alcohol poisoning.
Thus far Morgana and Gwen have been the only two characters we've ever see share a bed. Morgana also subconsciously rubbed Gwen's cloak when she's nervous (in Valiant) and Gwen was constantly bringing her bouquets of flowers (especially in The Mark of Nimueh.) Then there was this exchange:
Morgana: [Guinevere] is more than just my maid servant...(significant pause)...she's my friend."
Fast forward to season three when the two are no longer friends and the Foe Yay becomes palatable. After realizing that Gwen makes for good leverage over Arthur, Morgana gets incredibly touchy-feely with her what with fake hugs, hand-holding, and scenes in which it genuinely looks like she's trying to seduce information out of her.
Morgana's obsession with Guinevere is second only to the one she has with Emrys.
Katie McGrath even ships Morgana/Gwen. At Comic Con 2012, a fan asked about the conflict between Morgana and Gwen. Her answer is about as subtle as a trainwreck.
Katie: (paraphrased) There's going to be mud wrestling.
It all takes a very dark turn in The Dark Tower, but Morgana is still unhealthily fixated on Guinevere, at one point even calling her "my darling."
Miscellaneous Ho Yay
And this is all not to mention Merlin/Will. The reason why Will was so pissy was because Merlin found a new boyfriend!
Gwaine! Within minutes he and both Arthur and Merlin had formed "bonds". Slashy subtext permeated that entire episode. More than usual, that is.
When Gwaine wakes up, shirtless, in Merlin's bed the morning after their first meeting, and sees Merlin walk into the room, his first question is, "What am I doing in this bed?" Did Gwaine automatically assume he had sex with Merlin?
Can't forget the glorious Man Hug between Merlin and Gwaine in 3x08, where Gwaine was the first one to ever hug Merlin.
And in 4x02 when Merlin returns alive Gwaine gives Merlin a big hug.
What about Lancelot? Who didn't he have chemistry with in his debut episodes? Merlin and Arthur seem to have pretty serious crushes on him, Merlin practically fanboying all over him for most of the episode. This idea at least seems to have been sort of chucked out, given the pretty strident (and at times bewildering, mythical!canon though it admittedly is) Lancelot/Gwen versus Arthur/Gwen in Lancelot and Guinevere, but to be honest, this is Merlin...what's a halfway-canon couple one minute tends to be only a vague memory the next.
Oh, it's back. In the season 3 finale the gang sleep strewn about the floor of a deserted castle, but Merlin and Lancelot sleep right next to each other, close enough to engage in some pillow talk.
Season 4 practically makes them boyfriends.
To elaborate, Lancelot was worried over Merlin and wanted him to go back to Camelot where it was safer, especially since Merlin's magic didn't work against the Dorocha.
Lancelot was also the first to rush to help Merlin when Merlin collapsed at the feast.
And then he walked into what seemed like certain death for him; though arguably that was just as much for Guinevere as it was for Merlin.
In 4x09, it's back once more for one last time. When Lancelot is revived by Morgana and returns to Camelot, Merlin pretty much acts as if he got his lost boyfriend back and when he is the first (and only) one to notice something is different about Lancelot, he seems crushed. However, the ending scene takes the cake: Lancelot's funeral is suspiciously reminiscent of Freya's - who happens to be Merlin's first canonical love. It comes complete with Merlin's hand tenderly resting on Lancelot's forehead to work a spell on him, but whatever and Lancelot equally tenderly whispering "Merlin ... Thank you ..."
Merlin and Gilli. Dear gods, Merlin and Gilli.
The knights seem very affectionate towards Merlin. On the basis of the previews alone we've seen Lancelot carefully tending to and drawing a blanket over Merlin whilst he's injured on a mission and Percival carrying an unconscious Merlin in his arms.
4x02 features Gwaine/Percival. Including Percival knocking Gwaine to the ground, their faces getting very close and Gwaine making a crack about how he didn't know Percival cared so much.
Season 4 seems to be dedicated to include fanservice between all the Knights of the Round Table in every possible combination. In 4x06, there is a scene where the knights find old!Merlin/Dragoon in the woods and try to arrest him. Naturally, Merlin quickly knocks them out using magic, which ends in Leon, Percival and Elyan lying on top of each other in a mildly slashy way. On top of that, Merlin seems a little too pleased bumping Leon and Percival together chest to chest ...
Percival and Elyan seem to have a BFF thing going on. It's most noticeable during 4x01 with Elyan rescuing Percival rescuing three children and 4x13, when Percival breaks Gwaine, Elyan and Gaius out of prison. While Percival gives Gwaine a short relieved smile, he instantly walks over to Elyan where the two have a long and rather hands on reunion.
In the second part of the season 5 two parter opener, we have Merlin helping Mordred out of his cloak, talking about how if Arthur knew Mordred was a druid things would be different. It plays out like a man blackmailing another about his sexuality.
Let's face it, the moment we got Mordred as a young adult, the (eventual) Foe Yay between these two pretty much exploded, with many a Held Gaze and the link in every scene they shared.