Instructions
Complete the game's Adventure Mode for the first time.
Start a new game in Adventure mode and go to Level 4-10.
Wait for the Zombie Yeti to appear on the right side of the screen and plant pea-shooters to attack him.
Plant a Wall-nut or other defensive plant behind the Zombie Yeti once it is fully on the screen, as he will turn around and try to run away after around 12 seconds.
Inflict 75 points of damage on the Zombie Yeti to kill it and it will drop five diamonds, each worth $1000. It will now also appear randomly in other levels and Survival games.
Re-start the level and start again if the Zombie Yeti gets away before you manage to kill it.