Hannah Montana/WMG
The entire thing is All Just a Dream, and the main characters are in a secret government laboratory where ideal dreams with a limited number of scenes and situations are inserted into peoples' heads.
Think of how the stage on which Hannah performs looks the same in every episode. Also think of the heaps upon heaps of cliches and cartoonish behavior, how nothing has any real consequences, and how successful someone who only ever is shown performing on one stage would most likely be. Most of the characters - the ones for whom most of their personality can be found under Characters As Device - are not real, but are illusions projected into the test subjects' collective mind as their brains mash together in one machine in an experiment on how to brainwash the masses using television.
This experiment is also run by Susan Stewart, Miley's "dead" mother, on behalf of Disney.
Everyone is a paranoid schizophrenic.
Think: everyone overacts in this universe to a ridiculous level, and the Laugh Track runs nonstop. Could it be that they hear the disembodied laughter and deliberately overact because of the laughter in their heads?
This could apply to any show with overacting and a nonstop Laugh Track. Many SitComs.
- Or the scenery is covered in chocolate and they all want to eat it up.
- Well, Miley does say that she hears an imaginary Laugh Track in her head...oh god, you're right!
Her wig is hypnotizing.
How else would the most popular kid singer ever be made unrecognizable with only a simple change in her hair style?
- In that case, Robbie's fake mustache is also hypnotizing.
After The Movie, the people attending the concert signed ironclad Non-Disclosure Agreements
Most of the townsfolk were quite willing; but in case they weren't, the mayor had the cops man all exits, where Hannah's lawyers were waiting.
- all their facebooks are checked...twice a day...
The series takes place in the 1980s, and Hannah/Miley is the otherwise-unseen mother of Troy Bolton
- Except she is, like, the third character seen in HSM, and appears regularly on the others.
Hannah Montana is the antichrist.
She is here to harvest as many children as possible during her "concerts" and replace them with demons who will eventually take over their parents who will all band together to destroy the world. This is her Evil Plan. She uses her antichrist powers to make her music popular and to somehow look completely different just by wearing a wig.
This also supports the popular theory that Disney is evil.
Everyone already knows
Here's one. Pretty much everyone who cares already knows that Miley is Hannah; but Robbie Ray has made it clear that if ANYONE spills the beans in public, then he'll forbid Miley from performing. Faced with the mass revolt of every under 11 year old girl on the planet (and all those for whom Hannah is a Guilty Pleasure), the media has agreed to keep mum.
Hey, they're willing to pretend Santa Claus is real.
Miley doesn't have a normal life
Robbie Ray, realising how unlikely it is that a teenager could keep a secret like this, hired a pair of actors back when he first moved to California. They agreed to be Miley's friends and to give her the illusion of a normal life and allow her to slip up and spill the secret without risking it coming out. These actors, playing characters named Lilly Truscott and Oliver Oaken, have been pretending for so long that they are Becoming the Mask.
Miley is allied with the Jonas Brothers in a Evil Plan destroy all good music.
This one doesn't need much explanation. It applies to the real-life Miley, too.
- Expansion: Disney is allied with the Rhombulans to defeat the Elite Beat Agents.
Rico Will Be Disowned By His Father.
Because he wants to play football instead of running the Surf Shack. He fails at becoming a football player because his coach didn't put him in the championship game and makes money selling things door-to-door out of a van instead. And then one day he gets a call from his estranged mother saying that she's in the hospital and needs someone to take care of her grandkids-Rico's nephews-Kip and Napoleon. Ignore the time issues and it makes sense.
The Stewarts are aliens
Hannah's mundane alter-ego Miley Stewart is, in fact, a ruse to draw speculation away from that fact. In order to maintain the charade, The Men in Black had to track down and neuralize anyone and everyone who had seen her blow her cover in Tennessee.
Miley has Mulitple Personality Disorder
The whole show is taking place inside her head, and she just hasn't noticed it. Everyone knows her "secret", and everyone who admits to knowing it does so to make her feel like it's real, so as to avoid her going crazy. All the Hannah publicity is faked. It's so because Robby was famous, and his daughter's didorder was in all the tabloids. He did it for her sake. In other words, the secret she keeps form everyone is really being kept by everyone from her.
Hannah Montana is not human.
She is, in fact, the physical protrusion of some sort of interdimensional horror. She has been living in our world for long enough to be under the delusion that she is actually a person, but at the end of days, she will be forced to fulfill her dark purpose and unlock the gates of oblivion to release her true form from that dark void between realities.
She will do this by singing 'Party in the U.S.A.'.
Miley was set up to fail in "Come Fail Away"
Having Hannah Montana (as opposed to a real voice actor) perform the role of Dinah, the Determined Duck was a cheap publicity move foisted upon the director by the studio brass. The director had no intention of letting Hannah perform the role. He set up the situation so that either she would quit, or he would have ample justification to fire her.
Mikayla is Alex Russo from Wizards of Waverly Place.
That's So Raven and Wizards of Waverly Place have had separate crossover episodes with Hannah Montana, meaning that psychic and magical abilities exist in this universe. Alex Russo somehow discovered Miley's secret and, intrigued, used spells to create "Mikayla" so she could see what leading a secret popstar life was like.
Every interaction Mikayla had with Hannah/Miley was just Alex doing it for kicks. She was just pretending that she hated Hannah because it was more fun that way - especially since she eventually befriends Miley (as her own inside joke).
This explains why we never see Mikayla after Season Two. Alex got bored with the game and erased Mikayla from everybody's minds.
This is also why nobody has yet to figure out that Miley and Hannah are the same person. The illusion is now aided by a spell on the wig cast by Alex, her last gift to Miley.
Finally, this is the reason Alex completely avoids Hannah when they are both on the S.S. Tipton (during the Wizards On Deck With Hannah Montana crossover). She is afraid that Hannah seeing her will break the Forget spell she put on Miley and Lilly.
It's a literal case of A Wizard Did It.
- Hannah changes wigs between Seasons Two and Three. In the same crossover episode where Alex and Hannah are on the Tipton, Hannah conveniently loses the wig she is wearing to a gust of wind that came out of nowhere. Unknown to the audience, this was caused by one of Alex's spells. Robbie Ray gave Miley a spare wig; Alex put a spell on it that makes people believe the person who wears it is Hannah Montana. She sneaked into Robbie's room earlier to do this. He spent most of the episode completely incapacitated by seasickness, so he didn't notice.
- We can go even further and attribute every continuity error in the series to Alex's meddling with reality.
- This is further supported by the Shakira episode of Wizards of Waverly Place.
Miley has a Piece of Eden.
This explains the disguising powers of her wig (it may even be the wig) and possibly her phenomenal success. Considering the sheer number of historical figures that have possessed Pieces of Eden over the years, it's plausible.
Miley's father spends all her Hannah Montana money.
- He lies to her and says he's putting it in a fund for safekeeping. In reality, he spends the money on hookers, drugs, gambling, expensive trips, and possibly bribes to the mafia to keep other female pop stars down to reduce the competition for Hannah Montana. (thus ensuring that his money train will keep going) This explains why it doesn't appear she has a lot of her own money to spend, most notably in the Credit Card Plot episode where she's given a credit card for "emergency use only". As is common with the plot, she goes on a shopping spree which wouldn't even be considered a drop in the bucket for a multi-millionaire. But it's such a big deal to everyone. This also explains why she doesn't have a chaffuer. She would often whine about how Jackson had to drive her everywhere, but again, she should easily be able to afford a chaffuer so it shouldn't have even been an issue.