Grace isn't dead.I wouldn't put it past David Blood to lie to Rich just to get him away from her...
Matty is a hardcore stoner.It explains his Dull Surprise and monotone, and his actions in the pilot of season 5- he comes across Franky and, in his drug-addled haze, hangs around despite the fact that she's distraught and wielding a gun. It also explained why he looked surprised when he said she was beautiful- he'd actually had a coherent thought.
Rich was institutionalized after Grace died.His disappearance is never fully explained even in the extended on-line content. The Lit teacher is over the top nice upon his return and he looked like he was going to confess something when Liv freaked out at him and screamed "Why aren't you in the loony bin?!" A six week stint in an asylum to deal with massive depression would explain why he was gone.
Cassie is an alternate universe version of River TamOr a distant ancestor or earlier incarnation of her. I mean, seriously, they are very similar characters - both very intelligent to the level of being scary-smart (tell me the thing that Cassie did with her A-level exam of seeing how long she could wait to start "and still get an A" isn't something River would totally do) but very mentally-disturbed, and also Cloudcuckoolanders, and Cassie's ability to read people and manipulate them borders on the psychic (see: the scene where she tells Jal she knows she's pregnant - as far as we know, Jal hadn't told anybody by that point). Also, they share the same basic body type, even if they have different hair colors, faces, etc.
Effy is a Time LordBecause somebody has to be. But what would her TARDIS be? That stuffed giraffe?
The characters who die each generation are all Time Lords and when they "die" that's actually them leaving and just creating a new incarnation of themThis would also explain why Alex made his first appearance the episode right after Grace's death, he really is replacing her in the gang as the resident Time Lord.
S5!Franky and S6!Franky are actually different peopleLike maybe Franky secretly has a twin and they've been switching off with the cast.
Franky is a Stepford Smiler who is trying different masks to hide her issuesLike Effy was. This would explain her personality change in S6.
Grace is a ghost in S6.That is why everyone halucinates about seeing her. They aren't all mad she is communicating with her friends.
Series 7 will NOT GO TO PLAN.Right now the plan is a special about each of the three gens. I submit that what we end up getting will be something different. For Gen 1 all we have is confirmation that Tony and Jal will not appear (and Chris obviously) and I really can't see enough strong links between the remaining characters for them to all plausibly still be in touch five years laster, or for any interesting stories to be made for them to have their own dedicated special. Gen 2 looks slightly more promising with the confirmation that Effy and Cook are set to return, but it's slightly off that JJ is interested in returning but hasn't been asked to yet. And it's confirmed that Matty won't be returning as he's busy being in The Borgias. From this it seems that some people they haven't bothered asking and others can't do it as they're too busy now. So if they're not asking some people about returning then either they've never planned to do what was originally reported, or they do but they're leaving it too late to contact their actors who will ultimately not be available to do it as most of them are otherwise occupied now.
Effy is a Puella MagiThe reason Tony recovered from his accident, and over time, almost completely? It was because of Effy's wish. The various personality shifts she had with each season were her trying to deflect suspicion from the fact that she was sneaking off at night to fight witches. She lost her mind in S4 because, by then, she had learned the truth about Magical Girls (that they are liches, and that they're destined to become witches when they fall into despair) and she was worried that in her new relationship with Freddie, that he would find out the truth about her and her eventual fate. So she almost fell into despair and turned into a witch herself, but her friends were there to save her just in time. Maybe Pandora is a Magical Girl as well (her wish was for a friend, who turned out to be Effy - or, in S3, her wish was for Thomas to come back to the UK) and she was the one who stepped in to save Effy.
Tony is the grown-up version of Selim BradleyI mean, they do kind of look alike, and Tony's massive ego and sociopathy would be explained by him being the personification of Pride.
The girl in S2:E6 "Tony" doesn't exist"Sort of like Fight Club, she is another side to Tony. Everything she does, it's actually him doing it. He mouths off to the douche-y teacher, jumps in the pool on his own, turns out the lights to challenge himself, and then masturbates in the stoners' dorm room, which is still an accomplishment, as he is finally able to get it up. Him having the tattoo when he gets home is meant to signify that he was the one who got it, not her.