Instructions
Go into the kitchen of the white house (the one in front of which you start the game), and get the paper sack that is on the table.
Open the sack, and get the garlic inside it. The lunch in the bag is for another purpose in the game.
Head for the coal mine, which is at the very northern end of the underworld map. For a shortcut, go to the southern mirror room, which is south of the round room, and touch the mirror to travel to the northern mirror room.
Enter the Bat Room, which is directly north of the Squeaky Room, making sure you have the garlic in your possession. As long as you have the garlic, the bat will stay hanging on the roof, holding his nose.
Drop the garlic in the Bat Room if you want to reduce your inventory. The bat will stay away as long as the garlic remains in the room one way or another.