As seen in the picture, Logan practically jumped into Kendall's arms when the set designer proceeded to demolish their apartment ceiling.
When the daughter of the record company exec, a Rich Bitch decides to date each one of the boys, Kendall seriously THROWS DOWN with her when she tries to date Logan. Because that's how you act when a pretty, rich girl who will further your success decides to date you/your friends.
While Camille is pursuing Logan in Big Time Party, his immediate response is to escape and literally jump between Kendall and his date Jo, begging him to help. To add to it, Jo, James, and Carlos all advise Logan to see where things go with her, pointing out that a pretty girl like Camille isn't really someone he should be running from; Kendall, on the other hand, nearly commands him outright to tell Camille that he isn't interested.
Logan again runs to Kendall and physically inserts himself between Kendall and his current love interest in Big Time Surprise.
This is for whatever way you want to interpret it:
Logan spends a lot of early season 1 episodes looking at Kendall as if he's the greatest thing ever. On top of that, outside of official love interest Camille who actively pursued him, Logan himself seems to pursue blondes (like Jo in Love Song or Peggy in Crush.)
Kendall seems to be attracted to Lucy the most when she's wearing a brunette wig and acting more polite and bookish to please her parents, and Logan is known to be the group's bookworm.
The look on Kendall's face in Green Time Rush when Ozzie snaps up Logan as his partner. Everyone else looks terrified, Kendall just looks kinda ticked off.
In Big Time Camping: Kendall running onto the set of the commercial which Logan has been mistaken as a costumed stuntman for, shouting "get away from Logan!" and physically grabbing and fighting one of Logan's attackers.
Similarly, in Big Time Movie, Logan rescues Kendall from Maxwell and his silver hammer.
In episodes such as Big Time Crib, Big Time Terror, and Big Time Jobs, Logan clings to and hides behind Kendall in the face of danger.
Big Time Bad Boy: When Kendall poses as the band's "bad boy" complete with proper attire, Logan blatantly looks him up and down (twice!) and licks his lips.
In Big Time Break Logan bursts through the apartment door in a tattered dress, and Kendall's jaw-dropping reaction is noticeably different from the other characters. After Logan collapses and they all run to his aid, Kendall stands behind him and appears to be looking up his dress.
Kendall hiding his figure skating shame in Big Time Secret could be seen as a metaphor for hiding his sexuality. Logan is meant to be jealous and outraged at Camille and Kendall sneaking around, but Logan does not share a single scene, dialogue exchange, or even make eye contact with Camille in the entire episode— his anger and betrayal is focused completely on Kendall.
When Logan questions Kendall about his whereabouts and the latter supplies that he was just doing "stuff," Logan (frighteningly) informs him that he likes stuff too. Keep in mind that Logan fully believes the "stuff" Kendall is referring to is romantic or sexual in nature.
Kendall's face when Logan tells him that they're proud of him (after revealing his "secret") is heart-melting.
In the episodes Big Time Move and Big Time Breakout Kendall is forced to reunite the group after splitting up, but he focuses more energy on bringing Logan back to his side and seems convinced that he can't do this without Logan.
Kendall has called Logan "Logie," a nickname only used in-universe by female characters (both of whom Logan was on a date with at the time.)
A fan tweeted this to Carlos and James. A certain band member retweeted◊ it.
They tackle each other several times.
In Big Time Mansion, Carlos accidentally knocks over James' glass of chocolate milk. It ends with James knocking over Carlos and fighting on the floor.
In Big Time Reality, James and Carlos "fight" because the producer wanted something exciting. They roll around on the floor alot. At one point, Carlos ends up straddling James.
In Big Time Secrets, Carlos tackles James through Lucy's apartment door and ends up straddling James while fighting.
James spends the duration of Big Time Secret trying to help Carlos get the phone number of a childhood crush James once ruined his chance with. When the girl gives Carlos her number to give to James, Carlos struggles for a moment before ultimately giving it to James. While he is clearly excited by this, once James sees how hurt Carlos is, he throws the number away and tells him it's not worth it.
In the same episode, the two glue their hands together twice, leading to multiple scenes of the two holding hands. What's better is that none of the other characters ask why they're holding hands or seem too concerned by it.
Carlos has instinctively grabbed James' hand in quite a few episodes so far. See here.
Taken Up to Eleven in "Big Time Beach Party" (as seen in this pic◊) where Carlos is focused on James even though all of his friends are cheering Kendall on in an ATV race, and James is with his girlfriend-of-the-episode.
In Big Time Decision, Carlos turns down Bitters' cash offer for his second bottle of Zom-B-Gon, stating that James is his best friend and "I want him by my side." Moments later, when James accidentally drops his bottle and reacts in distress, Carlos lets his own bottle shatter along with it and states that he would rather be a zombie with James than be human without him.
In Big Time Double Date, James spends the night interfering with Carlos' date to make sure it goes smoothly; Carlos is outraged by his meddling and comically pushes him away on a dessert cart. Afterwards, they all perform the song Cover Girl, during which James sings the line "I would do anything to make you smile" and the camera lingers on Carlos gazing up at him. In their next scene, Carlos is very happy with James, calling him the best bud ever; given that there was nothing between the anger and the make-up but the song, it suggests Carlos interpreted the romantic lyric as being about James and himself.
This quote from Double Date:
James: We've got to change those reservations and go on that date with Carlos!
Carlos seems to take James' absence the hardest in Big Time Concert, lamenting sadly after Logan's comment about the choreography being different with just the three of them that "Everything's different with just the three of us."
When James returns, Carlos runs to him and lifts him from the ground, mirroring the earlier reunion scene with Kendall and Logan and their girlfriends.
It is suggested twice in Big Time Rocker that James and Carlos could enter a threeway relationship with Lucy; both times, James has to check with Carlos to confirm that it would be weird.
Big Time Reality implies the two share a room.
Carlos has a habit of clinging to James' arm or shoulder; taken to the extreme in Big Time Moms and Big Time Single with Carlos very nearly wrapping himself around James.
In Big Time Cartoon Carlos leaps into James' arms in much the same way as the above example for Kendall/Logan— except Carlos simply does this because he's excited, and James gladly holds him for most of the scene.
That's how they celebrate getting new sneakers.
Big Time Girlfriends, which really brought the Jogan- big time. It was easier to believe Logan had been cheated on by James than Camille. And really, a Brokeback Mountain-esque spitball fight?
It was out in full force in Big Time Sneakers with all the hand-holding, groping, and rolling around on the floor. It was even Lampshaded in-episode, with Mrs. Knight catching them in compromising positions and taking a "I don't want to know" attitude about it. One wonders what that Running Joke was supposed to be if not this...
The entire episode of Big Time Songwriters.
Special mention must be made for how James and Logan came up with the lyrics to the "Yeah" song: Logan mentions that James is great with words when talking to girls and James agrees... then proceeds to look at Logan, dress him up in drag, and sing to Logan dressed as a girl.
James and Logan get an awkward, but very Ho Yay-ful moment in the new prom episode, which ends in Logan being Prom King and James in drag being Prom Queen.
And then they dance. Together. Yeah.
In "Big Time Tests," James has Kendall take a "Is He A Bad Boyfriend" test as if James were his boyfriend. James gets offended when the result of the test says that they shouldn't even be dating.
Kendall: A Pop Tiger test is not going to answer whether you're a good boyfriend or not! You're a great guy!
James: Really? Because according to this, we shouldn't even be going out!
Kendall: Uh...we're not going out.
James: Oh, oh, because I'm so terrible to be around, huh? Yeah, thanks.
Kendall: Maybe this was a mistake...
James: Really? This whole thing since kindergarten was a mistake?
James: No no no, have it your way. I'm out of here! (storms off)
In the season one finale, Big Time Concert, Jo kisses Kendall, and Camille dreamily exclaims that "wow, she is really good at goodbyes." Because that's exactly how friends usually react to their friends' kissing skills.
In Big Time Party, Jo remarks that "starring in Camille's fantasy movie could be fun."
Despite their first meeting consisting of Camille storming into the lobby to kiss Logan and threatening Jo, a few scenes later the two are lounging together by the pool talking, and shortly after that they're alone together in Jo's new room (which, it should be noted, Jo just moved into the very same day— she hasn't even unpacked, and Camille is already there.) This happens in the span of what could only be a few hours.
At some point Jo explicitly told Camille that she did not have a boyfriend. Perhaps she wanted to assure her of this before inviting her up to her bedroom?
Jo and Camille both profess that they voted the other for prom queen, as a contrast to the boys who are obsessed with winning themselves; Camille even seems to flirt with Jo a bit when she tells her.
Jo and Camille share hugs in Welcome Back Big Time and Big Time Beach Party.
When Camille announces that she will be able to stay at the Palm Woods in Big Time Video, Jo claps briefly then clasps her hands together and looks to the sky in gratitude.
Both Jo and Camille have the first instinct of showing the other their new necklace in Big Time Gold and seem as eager to be with each other as they are to be with their boyfriends. When they figure out the boys' attempted Zany Scheme Camille suggests splitting the necklace into two bracelets, allowing them to have matching jewelry, and Jo suggests merging her birthday dinner with Kendall and Camille's anniversary dinner with Logan into one shared dinner.
Camille clings to Jo for safety when the Black Ops arrive in Big Time Pranks II, amusingly gender-bending the common occurrence between their respective boyfriends.
Erin Sanders (Camille) has acknowledged a Jomille fan on Twitter and responded to questions about the ship with a flirty wink.
At the end of Big Time Rocker Lucy is nearly knocked over in the group's struggle to fit through the door and Camille wraps an arm around her waist to steady her.
Lucy informs Camille that she "looks hot" in Big Time Surprise.
The episodes Big Time Scandal and Big Time Lies introduce a new dynamic between Jo and Lucy, who had previously only interacted once very briefly.
In Scandal, Jo claims to be angry with Lucy, but behaves much more sensibly and politely to Lucy than Kendall, who only makes the situation worse. At the end of the episode, Jo is the only one to call attention to Lucy being "really nice" for helping them.
In Lies, Jo pretends she's fine with Lucy's return as Lucy secretly pursues Kendall, and the two extend friendly greetings multiple times, with Jo's feeling awkward and Lucy's more predatory. Jo confesses that Lucy's return made her nervous because she is "so pretty and talented." Lucy admits that she was faking her desire to get Kendall back for song inspiration, and seems to focus her apology more on Jo. Jo mocks Kendall's pants, and Lucy gazes admiringly at her before the two exchange more jokes and walk away from Kendall side-by-side (and what appears to be momentarily arm-in-arm.)
The ship set sail before the episodes even aired, with Malese (Lucy) tweeting this. (She even coins a Portmanteau Couple Name, which would later end up being used more commonly for James/Lucy.)