Why does Ojiro get angry from hearing the word "bakeratta"?
It appears one of the main characters of Obake no Q-taro is also called Ojiro. 

I thought Q-taro was the one who said "Bakeratta", so I was looking mostly at his character - but it is actually his little brother, Ojiro, who is the link.

He can understand everyone speak, but can only say "Bakeratta", Q-taro is the only one who understands what this means.



So I guess his Ojiro and his brother (in Megane X Parfait) watched it before, and made a joke out of it because they share the name.