Create
49 Achievements
1,000
30-35h
Xbox 360
Pop!
100 balloons burst
10
How to unlock the Pop! achievement in Create - Definitive Guide
This one is easy. Go to a scoretastic challenge where you can use lots of different pieces. Place a row of balloons with spiky balls above them; press start and they'll pop. Now press start again to make re-appear. Repeat until achievement unlocks.
Lots of challenges use balloons and pop them; this will be unlocked in the course of normal gameplay.
This should come naturally as you progress through the game, but if it does not and you want to boost the best way to do this is similar to the Toaster method. Load up any challenge where you can use any object and place a row of heavy items (like an Anvil) somewhere. Now attach balloons to all of these objects and above these balloons place a Burster (the spiky metal ball). Start the challenge and wait for the balloons to pop, then stop the challenge and continue restarting it until the achievement unlocks.