The invention of lying.
SPOILERS DONT READ ON:
I didn't like how he didn't make smarter and more proper use of his discovery of lying, why on earth didn't he bang that woman at start ish when he said the world would end, why didn't he retreat a gazillion dollars and buy whatever he wants including a collection of hundreds of cars, planes, boats, etc ? Did he have to come up with that stupid ''god'' ( man in the sky) story? Why didn't he pay attention to what he said while others were near for example in the hospital when near his mother ? I was basically just facepalming the whole episode of his stupidity. 6/10 for the idea and I did laugh a few times at start, but after that, unrealistic actions and a main character I can barely relate to.