Throughout many years, I've been trying to extract these files for both Club Penguin DS games, Elite Penguin Force and EPF: Herbert's Revenge, with no success. I've tried a variety of methods, even some very unusual ones, but I've never been able to even come close to explore them.
Maybe, in the near future there can be a way to check what's in these files, and finally extract the graphics and music from them, but for now, there seems to be no way of doing that.
Maybe it's possible for a plugin to check these files out? I'm not very knowledgeable myself, but it would be really nice if possible.