The series is set in the hedgeThe clubhouse members are either a very powerful motley or a very small goblin market, the world around them is strangely both fluidic and consistent, several subtext laden lines hint at pledge and contract use, and the degree of clarity/sanity clearly varies from episode to episode.
The Clubhouse was originally built as a military fortessProbably the best explanation for many of the things that are noticable in the Clubhouse itself. Many years ago, there was a war. One of the sides had access to technology so advanced that no normal man could replicate it. Using the technology, the army of that side built what they called the "most advanced fortress in existence". The fortress consisted of a central "hub" with many "rooms" attached to it. These rooms had the ability to fully compact themselves into small packages of metal, wire, and gears; which can then unfold for later use. The hub was also able to "flip" itself, and the rest of the fortress, into the ground. These two abilities can be used to completely bury the fortress in the ground, avoiding it's detection by enemies. Inside the hub of the fortress was a supercomputer, which was often called by the military "the jewel of the fortress". The computer was designed to compute the possible outcomes of the war, and also had the ability to send tools to the armies in battle, via a mobile, computerized probe. Eventually, after the war was over, the fortress was sold via auction by the army that used it, and the highest bidder was: Mickey Mouse. Mickey refurbished the fortress into a clubhouse, and that is the story of the Clubhouse itself.
Everyone's a robot.Generally they're really good and fluid, but towards the end of the show (and certain parts throughout) they go through preprogrammed motions. Also explains any character differences; it's not actually the characters we know.
The entire cast is finally showing their old age.That's why they all have to ask what things are, can't find things in plain sight, are forgetting people and basic things like math (except for brief flashes). Also might explain Pete's Character Derailment ; he's mellowed out. Alternately...
The entire cast is children...... and all of their adventures are just them playing pretend. This explains their constantly changing roles, nicknames, rules of the fantastical stuff, and Pete shifting from ally to enemy depending on the story. Professor von Drake might either be another kid, or he could be their caretaker/babysitter who partakes in their games. In a way, looking at it this way makes the show a bit more interesting. It's a Muppet Babies style show, from the constant point of view of their fantasies.
Mickey is in a comaIt would explain why every aspect of the clubhouse, and many aspects of the world are centered around him specifically, from the clubhouse itself, to Toodles, to the most powerful energy source yet seen, the Crystal Mickey. It would also explain why the characters are completely fine with Mickey's somewhat narcissistic attitude towards always being the main hero or a very important main character in nearly every single adventure they go on, to the point where they chant theme songs ("Kansas City Mickey") for him without fail. This also explains why everyone is able to pick up on the random songs that are written throughout the show, despite not having ample time to fully learn them, if any at all. If this is all in Mickey's head, and he spontaneously comes up with the song, than all of his imagined characters would immediately know it as well. This also explains the lack of sense in the world's physics, the fact that Pete is sometimes bad/sometimes good, and that the Clubhouse seems to be omnipotent. The "challenges" Mickey goes through are his brain trying to keep himself active by forcing him to think. Toodle always has a perfect set of Mousketools for the challenge because the challenges were planned ahead of time, even if Mickey's in-universe self (or his conscious self) is unaware of it. The clubhouse is his unconscious mind trying to keep Mickey going through the coma and prevent mental activity from stopping altogether. The times when the Cloubhouse stops working (like the aforementioned Kansas City Mickey episode), are instances where Mickey is on the verge of becoming braindead, and you can notice that these problems tend to take longer, or require more effort to solve than most of his other challenges. The entire show is Mickey fighting in his subconscious to stay alive, using the clubhouse and his imagined characters, likely based off of his real life friends, as mechanisms with which to fight his way free from the coma.