Do you think Mario is a plumber?
I believe so. The first game from my understnding is called Plumber man.
Did you hear about mario's death? How can mario die?
I did. Its time for Luigi to take over since Nintendo decided to kill Mario through terrible marketing. 
Yea, I still confused to how a digital character can die. But I don't think a lot of people know about Luigi.
I disagree. Luigi's Mansion is a great game and they just released the third one. 
Is Luigi's Mansion about catching ghost?
Its about catching ghost as well as trying to free your friends from King Boo
Are the Boss fight tricky compared to the other Luigi's Mansion?
The games are more for enjoyment than they are for difficulty. Boss fights are enjoyable.