The Simpsons: Tapped Out has a bunch of characters for players to unlock. Among them is Grampa Simpsons, Homer's father and crotchety old man.
1. Open the game on your device by tapping on the particular icon.
2. To unlock Grampa Simpson, you need to reach to level 19.
3. After reaching to the level 19 you will be able to unlock the Retirement Castle.
4. After unlocking the retirement castle, you will be able to unlock Grampa. Grampa is the final unlockable character in the game. Getting to level 19 is a grind, but he's the reward.
5. Once you unlock the Retirement Castle building, you need to complete construction on it to get Grampa into your Tapped Out town.
6. The building does not provide you with income. It will, however, unlock quests for other characters in your Tapped Out town. Grampa will give you income from his daily earnings.