Keanu is secretly a robot
While the majority of people are at least able to see that Keanu behaves in a manner similar to that of a living object, even if the living object in question is a tree, others go so far as to deny Keanu's biological status and claim that he is, in fact, a robot.
Putting aside the resulting problems such as how he then managed to conceive a child – and if the governmental scientific organisations have knowledge on human-robot reproduction which they are craftily hiding from the populace – there are also other issues with this claim.
Firstly, there are the many varied accidents that Keanu got himself into over the course of his highly interesting lifetime spent largely on motorbikes. He's ruptured his spleen, injured his left ankle, obtained an impressive array of scars and injured his spinal cord – resulting in a need for a medical procedure to insert a metal plate into his spine and cause him to go around with a neck brace for the first part of the Matrix shoot. We do have to admit that 'metal plate' sounds suspiciously like a robot replacement part, but, on the other hand, 'spleen' does not.
Secondly, we have behind-the-scenes evidence of special effects shoots for Bill & Ted's Bogus Journey: namely the parts in which Keanu played the evil robot Evil Ted. Why would they have blown so much cash getting these sequences right, and then shown us the process of how they made some supposedly human dude look like a robot, if he could have simply been himself?
Whereupon you might logically point out that there are no levels that studios will not stoop to in order to look as though they need more money.
However, that film shoot was in fact scaled down from its far more expansive (and expensive) original vision. So, they were clearly interested in saving money, and that goal would have been greatly expedited by using a real robot in its original form, rather than making a robot look like a human trying to look like a robot.
Then there was The Day the Earth Stood Still 2008 remake, where Keanu was casted not as Gort the robot, but as his bodacious alien pal Klaatu. Articles on TDTESS are full of accounts regarding the amount of time and effort that special effects people took in getting Gort to look just right. It took thousands of potential designs and a huge amount of work to create said being almost entirely on the computer.
Why bother, if they had a real life robot right there in their cast?
In a similar argument as to why Keanu is not a tree, but perhaps with more relevance here, Keanu has been often spotted eating lots of food of the human variety. Sandwiches, steaks, coffee, wine, pasta, caramel-pecan chocolates, you name it. Robots don't need food.
Of course, it's very possible that it's all just a show in order to hide his true identity, but that begs the question of where all that food goes. Too much food in his non-organic internal system would, after a while, start to smell. While this might have contributed to the allegedly unpleasant body odour he was known for in the past, it is also important to note that said smell went away after a good shower, while the act of drinking water – which would have cleansed the metal bits inside of him – did nothing to help at all. But, you might point out, perhaps this was all part of the plan to hide Keanu's true nature, and They developed a custom artificial digestive system for him just to keep the deception going.
Conclusion: either Keanu is not a robot, or the conspiracy runs deep.