I dunno, this might be something that's well known already, but oh well.
In Ropey Rampage, after being blasted out of the first bonus barrel's exit, you'll find a platform with a patch on it which can be uncovered by jumping from a tall height.
Anyway, jump up onto the tree left of the platform with Diddy, then cartwheel jump up to the high tree on the right, just offscreen. Cartwheel through the rope, then jump when you're at the bottom of the screen and about to die and you'll appear back on the rope.
Edit: Think it works with any rope that you can cartwheel through the middle of, so yeah... I guess this one was found out when the game was released.