-go to the Prism Tower
-get on your bike
-set the direct of your bike to cycle around the tower
-put a coin underneath the circle pad
-bike will move by itself around the tower
Hey presto, eggs hatched.
You can just do it manually around the tower, but the coin can be used if you want to multitask.
EDIT: I read up a bit on this, and found that a bit of cardboard will be better than a coin. The coin might ruin your circle pad.