Gotcha! is an achievement that can be obtained on the iOS and Android versions of Plants vs. Zombies. To get this achievement, the player must use the single Plantern in Ace of Vase or Vasebreaker Endless to reveal a vase with a Gargantuar inside.
It is mostly based on luck, but if you find a Plantern, use it in the center of eight vases, so there will be a higher chance of finding the Gargantuar. If you want to, you can restart if you do not find it. Doing this each time will increase the probability of getting Plantern.