These have probably been answered before but I just got the Dark Knight and watched it again and had a couple questions.
1) Why does the Joker tell 2 different stories of how he got his scars? (One story was the his father did it then the other had to do with his wife or something)
2) Why does the Joker put a canister that looks like a grenade of sorts into Barry Pepper's mouth at the end of the first scene? Why does it just smoke and not blow up?

