Mexico has always been a troublemaker. When Spain looked after him he didn't stop pulling pranks on the conquistadors and Spain. He was a bit more cruel with his pranks as he didn't like the Spanish so he often used more harmful pranks than usual like shooting pins and needles or draining chili seeds over one's eyes. This usually got him hit with the belt or sometimes even whip.
Once he pulled a prank on Spain that was so awful that Spain ended up chasing after him yelling at him with profanities. Mexico ended up running for two days until he finally got caught and got one of the worst beatings of his life that he has small scars on his arms and upper back. They are noticeable but they are there because of a prank he pulled.
Just because he is older now doesn't mean he moved on from his prankster days.