There are two ways to get this, Use the Split Up Pad for the First time, (which would be Witchyworld the third level) or Hacth a Stop 'N' Swop Egg with Heggy. The fastest way would be Heggy, since Heggy is right next to the JiggyWiggys Temple. Ok, to go to Heggy, Go to JiggyWiggy's Temple's door, Go straight down from there. There is a gaint egg house, Heggy is there.
In case you don't have Stop 'N' Swop you have to go to Witchyworld, again, the third world, To use the split up pad, go to the tent entrance, go around to the back of the tent (don't go inside) on the back side of it, is JamJars, He will teach you Split up, next to him is a split up pad, Use it and achievement unlocked.