I attempted random koffins over a 2nd time to see if anything would change and of course to see if you could basically doup koins. I did not get anything new on either the PS2 or Xbox version.

yeah i thought about this too. seeing as it saves eveytime u open one (even the second time) it's very possible. i think that would be a great code if u unlocked something buy opening certin graves in a certin order the second time round.

Opening the Kaskets 2 times will do nothing. I tested this a little bit on the ones that give you koins but your koins will only increase the first time that you open the kasket. I'd assume it would be the same thing for every kasket.

Yeah i held off as long as i could to open the krypts. So right off the bat i did the names. noob siabot, ed boon, mortal kombat, rain, shao kahn and a few others. Of coarse you have had to find most of the keys to do this, since most involve key/koin kombonation to open them in order.
Unfortunatally they didn't go off the MKDA crap about the names to open koffins. I have not seen anything new from doing it. A bit disappointed, but the game is still a good game.

yes, tried even chased the people around in the krypt,to see where they go,and opened those and i got nothing,