Flaws in Karl's reasoning
As we know, Karl has a rather idiosyncratic view of the world. His understanding usually falls down for one, or many, of the following reasons:
Inability to see the bigger picture
Karl is particularly quick to dismiss things without considering how they are applied. For example, he dismissed Newton's explanation of gravity with, "if we were floating around, I'd be worried about it". If a concept seems too big for Karl to understand or perceive, he will often return to his own more easily accesible opinions. When posed with Descartes theory 'I think, therefore I am', Karl dismissed the concept stating "Why has he got the time to worry about it? Am I awake or asleep? You might as well be asleep because you're doing nothing else!".
Looking at everything in relation to himself
More specifically, Karl fails to consider how things may affect people other than himself - as evidenced by the quote: "MC squared (sic), I've never used it, whereas the guy who invented the video, I watch one a week". Karl has also expressed a lack of understanding to why we refer to our planet as the Earth, claiming he can't think of a reason to name it anything other than 'The World' since he personally has no need to reference our planet in relation to any others ie. Mars.
Applying human characteristics and consciousness to everything
Karl has a tendency to anthropomorphise. The main reason he can't get his head around the Infinite monkey theorem, is that he can't get over the idea of monkeys not understanding Shakespeare. Similarly, many discussions of creatures include the line "whoever made them...". Pretty much all of Monkey News also fits this description. It would appear Karl is largely incapable of perceiving conciousness on any other level other than that of human conciousness, therefore he applies the same level of social/moral human reasoning to the actions of animals, and in many cases even insects. Interestingly, Karl has often seemed to give more praise to his imagined motivations of insects and wildlife, than to the actions of famous inspirational historical figures ie. "Rosa Parks was lazy" or "Anne Frank was a squatter with a diary". Much to the annoyance of Steve and especially Ricky, Karl will even apply humanised states of concious action to his own different body parts such as his eyes, ears, nose etc. One of Karls most common questions throughout his career with Ricky and Steve has been "Who's in charge, me or me brain?".
Valuing the interesting over the true
Karl is seldom interested in whether a piece of information is true or not - he tends to believe things if they interest him, if they're "a bit weird". As such he's usually skeptical of any of Ricky and Steve's facts, but completely credulous when it comes to any ghost stories off the internet. On one occasion, Ricky referred to a documented study on chimps who would pick lice off of other animals and then place them on themselves to receive a 'free grooming' simply because they enjoyed the sensation of being cleaned. Karl, unimpressed by an actual fact about chimpanzees, responded "Yeah, its alright but I've got better stuff later on".
Fear of variety
Karl has an unusual obsession with cutting down waste and variety on the planet. He is continually trying to cut down the number of animals, people, plants, shops, etc. This was most promiment in the Do We Need 'Em? feature.
Lack of thoroughness
Karl tends not to investigate his stories and facts too deeply, believing that the headline gives you all you need to know. As a result, he often misses the flaws which Ricky and Steve pick up on, and he is usually unable to answer any questions they might have. It is uncertain to whether this is a result of lack of interest, an overactive imagination, or even if Karl simply lacks the capacity to pay attention for any sufficient length of time to an article. On several occasions when questioned by Ricky and Steve on his information, Karl would attempt instead to provide a brand new headline on a different topic. Ricky refers to this as "the intellectual equivalent of running away".
Karl's favorite fallacy; confirmation bias is when you try to use a single event as proof, ignoring the giant majority of time where the "idea" isn't true at all, or there is at least no reason to think such an "idea" to be true. Karl does this so much, that often Ricky and Steve suspected that listeners of the shows and podcasts might have been simply feeding Karl spurious claims and tales simply to mislead him on air. On several occasions Karl has recited an email sent to him containing nothing more than a popular joke which he then believed to be a true account of a person's experience, even when all logic would indicate otherwise. Karl has often defended his faith in these stories saying "Well, its written down innit."
The above leads to a lot of gaps in Karl's stories, and in filling them his imagination runs wild. A lot of the more outlandish stories in the shows have come from Karl's guesswork or wishful thinking.