Only appeared in demoOnly1.
"Only after collect all DK coins, the final course is open."(Bowser castle or Luigi castle is not final course.) ~ Carol
DK Coins are items that will be collected in the final version of Brutal Mario to enter the true final course. They are in reference to Donkey Kong Country, in which the coins were used in a similar purpose.
This is the first demo which the DK Coins began appearing. Though there is no point in collecting the DK Coins, as the game is yet to be finished.