The Theories and Rumours are things are any of this True (Theories) or False (Rumours).
Theories
Purple Guy has the God Friends
This is a very rare theory because at 2005, Purple Guy feels lonely and he never have anyone to hang out, until when he first have Emily, Wallace and Gromit, he feels sensitive and it is very unfortunate for the series because after the god friends finished with Purple Guy and the next person was Katie Sandow, he was pretty evil and angry and he's secret goal is to get Emily, Wallace and Gromit, so yeah it's pretty much weird.
Focusing on Katie Sandow
Katie, the main character of the wiki series. Fans always believe Katie always has the missions of every episodes, however, Most of the time she does, but not all shows, because in rare episodes, the show mostly focuses on other characters who has a major appearance besides Katie. Katie actually gets the main focus than other characters, but in the final episode "Katie, Emily, Wallace and Gromit: Katie's Last Stand", the movie focuses on Katie and GLaDOS through the whole episode-movie.
Rumours
Purple Guy, the Main Villain
When the show starts, Purple Guy was originally going to be the main antagonist in the series. However, He's ability was going to torture and killing children until When Vicky takes it's place and Purple was going to destroy Katie Sandow but Katie thought Victor Quartermaine will be the main villain because Victor is cruel, spoiler and pretty much eviler. So this turns out for purple guy to be fake.
The Heroes' Nightmares
This was a strong rumour for this, but it was actually a hallucination dream, the reason why it was that because the nightmares was never actually happened but one of the animatronics must of put the drug coffee before Katie and her god friends start the job and after they go to sleep. Which makes creepy much hard to think because the dreams for what each person has nightmares from the drug dream in each 1 nights.
A Big Fantasy
This is really big rumour. Many fans point out this is all of Katie's fantasy dreams (Day Dreaming, sleep dreaming or hallucinating.) She has a creative mind and such weird, adventurous and toxic ways that she thinks. In "Katie, Emily, Wallace and Gromit: Katie's Last Stand", the alternative ending was GLaDOS sets Katie free, by waking up her dream that she was "trapped" in, However it was cut out because they will think Katie has a issue disorder, so it just turns out of her real fantasy instead of a dreaming progress.