Posted this on the to do list thread before noticing this one : S
Sorry about the repeat, but i think its best posted here:
Not sure if this has been noted before or if its not a glitch, but in the Kirby area, when you're being chased by the rolling spike wall thing, you get to the 'second' screen of the chase (there are three apples in the bottom left corner, and you exit top right), you have to jump over a spike about halfway, and if you time it weirdly, you get a boost from it, like a normal jump, but to get over it, you need to double jump, so it can't be anything like that :S