Collect all the red diamonds in a world to unlock stage 10 in each world.
Stage 9-1
Successfully complete the game without using any continues.
Stage 9-2
Successfully complete stage 9-1.
Stage X-1
Use the warp block located directly above the starting position in stage 4-3. Note: Use bubble gum to get there.
Stage X-2
Reach the first checkpoint flower in stage 6-7. Continue to the right until you find a bazooka bee. Bounce off its back to find the warp block to stage X-2.