Hat WearerG 25

You can unlock this almost immediately.
If you look to your right when you spawn, there will be a watering can next to an elderly lemon. Go pick it up.
Keep walking right and water the plant that's above and to the right of the blueberry. Pick up the Flower.
Now, head down to the bottom half of this screen to talk to a strawberry and give her the Flower.
She'll give you this Love Letter, which you will immediately rip up to unlock the Heartless achievement.
Then, head back up to the blueberry to talk to them and be given the Sun Hat (and unlock this achievement).