Bay. She's either a selfish bitch or a poor, neglected Woobie. Either way, she undergoes much Character Development.
Daphne: Poor girl with daddy issues and a hard childhood in the slums, or a self-absorbed, manipulative, boy-crazed girl who only cares about herself and what she wants, while struggling to focus on anyone's problems but her own?
Why she claims to be a vegetarian and still eats shrimp? Perhaps she is a pescatarian, and thought it's easier to say she is vegetarian than start explaining what pescatarian is?
Regina: a well-intentioned and caring mother, or someone who selfishly held on to a child that she knew wasn't hers?
Emmett: a misunderstood troubled teen with his heart in the right place, or an irrationally jealous person who borders on emotionally abusive?
Angelo: an estranged father hoping for a second chance, or a slimy criminal looking for a cut of the lawsuit? After the trial, it became obvious that it's the former. Regina admitted early on that he wasn't really as bad as she had described him to Daphne.
Season four raises the question: Did Tank intentionally have sex with an intoxicated Bay, or did he really think he had a green light?
Lily: Would she stay with Toby if not for the baby?
Some Ship-to-Ship Combat between the Daphne/Emmett and Bay/Emmett shippers got up to these levels. The more vocal D/E shippers would often take Bay's initial selfishness and Bratty Teenage Daughter tendencies from earlier in the series and turn her into a domineering vixen that has a ukefied Emmett under her thumb while completely ignoring her Character Development over the course of the season. On the flipside, the more rabid B/E shippers will twist Daphne up into a possessive and psychotic Yandere that wouldn't think twice to Murder the Hypotenuse, conveniently forgetting the fact that the worst things Daphne ever did were mostly a bunch of failed and largely half-assed attempts at Relationship Sabotage. Thankfully, it's died down with the passage of time, and from Daphne ultimately pulling a genuine I Want My Beloved to Be Happy in regard to Emmett and giving him and Bay her blessing.
Ty also received some, despite Bay and Emmett hooking up after they broke up, though that's thankfully died down as well. It was reignited when he returned during Season 2.
Part of the fandom went berserk when Simone (of all people) slept with Emmett.
After only a couple scenes together, Toby/Emmett has gained an impressive amount of shippers.
Female version:
Between Regina and Melody. Particularly underlined in several instances, such as Regina asking Melody to be her plus-one for the Kennishes' party or to her art opening.
Some Internet commenters have noticed that Bay seemed to have a crush on her tagging buddy Zarra. Toby later lampshades this at Bay's "un-Valentine" party.
Bay and Natalie have some excellent Belligerent Sexual Tension, and now it's canon that Natalie likes the ladies …
Invoked In-Universe when Kathryn and Regina pretend to be a couple at a book release party, in order to get one of Kathryn's exes to leave them alone. They keep going with it (and even kiss each other on the mouth) when they find that it also stirs up buzz for Kathryn's new book.
Jerkass Woobie: The new deaf kid, Travis. He's abrasive, rude, and gets on Daphne alot for no apparent reason. It turns out his parents, who are hearing, made no effort to understand him or communicate with him and Daphne is basically his only friend.
The Soup had fun with a scene from the pilot, where John is thinking about Daphne's disability, and hears an ice cream truck driving by while playing a tune. At night.
Regina discovering that she'll never be able to sign again would have more impact if she didn't voice all the time anyway.
The second season episode "Uprising" was touted as being almost completely silent (save for the non-diegetic background music), and almost entirely in ASL (with open captions for hearing viewers). However, the effectiveness of this as a storytelling technique is undermined for hearing viewers when Bay's Hard-Work Montage in the middle features a song with audible lyrics.
No Yay: Chef Jeff and Daphne's relationship. She was his underage employee and he knew it.
There's something brewing between the Wilke/Daphne shippers and the Travis/Daphne fans. After Wilke got Put on a Bus to boarding school, things only started heating up for the worst.
Travis/Daphne versus Jeff/Daphne. The episode "The Declaration of Independence" didn't help things any.
Now that Ty's back, it's Bay/Ty versus Bay/Emmett. In season 3, it's Bay/Emmett versus Bay/Tank versus Bay/Ty.
Seasonal Rot: This goes here, because more and more of the show's many Deaf fans are complaining that the actors are getting lazy and sloppy with their signing. To top this, according to several of the "extras" who saw behind the stage, there is an ASL specialist, and yet some main actors refuse to listen to the specialist and continue to sign in their increasingly grammatically-incorrect way.
Strawman Has a Point: Bay decides to go to Carleton, despite having little signing ability and making no apparent attempt to learn. This leads to slowing down class for everyone and the art program being cut in order to pay for an interpreter for the hearing students. Naturally, a group of Deaf students resent this, led by the bully Natalie. Bay complains that she is being bullied simply because she's hearing, and that it's not her fault, and she's portrayed sympathetically, or at worst, that she and Natalie are equally in the wrong. This ignores the fact that it was her decision to go to Carleton in the first place. She's the one forcing herself into a culture she doesn't respect. Furthermore, she personally did everything she was accused of, which makes the claim of discrimination absurd, and the worst part is that she never stops or even acknowledges that she did anything wrong (apart from hitting Natalie with a volleyball). Stephanie Nogueras, who played Natalie, said in an interview that like her character she'd oppose this in real life since it would be very disruptive for the Deaf students (though presumably not reacting this harshly).
Watched It for the Representation: This is a show that prominently features Deaf culture as several of its characters, including one of its protagonists, is Deaf, so many people who were Deaf and Hard of Hearing tuned in to see how the show would depict their mannerisms, culture, and community.
Take your pick. Bay, Daphne, and Emmett all have their moments. Bay feels she doesn't fit with the parents that raised her and think they like Daphne more, and she feels her birth mother chose Daphne over her. Daphne feels angry with Regina for not telling her about the switch and keeping her from the Kennishes, then has Emmett choose Bay over her. Emmett watched Daphne date other guys for eight years, before having her express her feelings after he started dating Bay. Not to mention the Lonely Piano Piece that plays when he can't understand what someone's saying.
Travis. His family doesn't bother learning how to sign or communicate with him, and Daphne connects with him. Later on, when it's obvious that he's got a crush on Daphne, she flirts with him and makes plans with him in order to attract Jeff, then ditches him to go after Jeff.
Everyone. The sheer amount of Dysfunction Junction for the sake of drama makes everyone have their moments of sympathy.
that like her character she'd oppose this in real life since it would be very disruptive for the Deaf students (though presumably not reacting this harshly).