"Bats About Bats" is the ninth story in Still More Tales to Give You Goosebumps.
Suzanne and Liz are walking to Suzanne's house for a sleepover. It's dark out and a bat swoops out of nowhere and dive bombs the girls. They make a run for Suzanne's house, but the bat stops swooping and the girls see a very pale blond girl standing there watching the bat flutter away. She introduces herself as Dorrie Morrow and says her family just moved into the neighborhood. Her parents are "bat scientists" which is why she's so interested in bats. The girls become friends and begin spending a lot of time together. One afternoon, Liza and Suzanne go to Dorrie's house. For some reason, they're shocked at the amount of bat paraphenalia in Dorrie's room. On the way home, Liz and Suzanne discuss how gross bats are and how much they hate them. This leads to the two hatching a plan to scare Dorrie at their next sleepover. The plan: Liz's brother Mike will dress up as a vampire to spook Dorrie. They have the sleepover and Mike scares Dorrie. Dorrie cries wee wee wee all the way home. But she forgives them the next day.
Halloween comes and the three go trick-or-treating together. Liz is dressed as a clown, Suzanne as a gypsy, and Dorrie as a bat. At the end of the night, they go back to Dorrie's house to sort through their candy. A bat flies in through the open window and attacks Suzanne's head. Dorrie grabs the bat and cuddles with it while berating Suzanne for scaring it. Then she tells the girls there's something in the basement that she wants to show them. It's her parents. When she said they were bat scientists, she meant it--they're giant bats in lab coats.