Jessica and Elizabeth are about to get the scare of their lives . . .

Steven Wakefield has had it up to here with his twin sisters, Jessica and Elizabeth. Ever since the boys in their class at Sweet Valley Middle School challenged the girls to a Scare War, the twins have been driving him crazy: they’re busy coming up with schemes to scare the boys - and they’re testing them all on Steven!
So when the twins and their friends have a slumber party, Steven figures he’s really in for it - who knows what kinds of stunts the girls will pull? But Steven’s got some spooky plans of his own. One way or another, he’s going to out-scare them all!

A human guinea pig . . .

"It seems to me that we have plenty of interesting suggestions about ways to scare the boys," Janet said. "I think we should try some of them out first."
The girls looked at each other. "Try them on who?" Amy asked.
"We need a guinea pig," Janet explained. "A human guinea pig that we can test these scares out on."
"It sounds OK to me," Maria said. "But where do we find a guinea pig?"
At that moment, a dreadful noise came floating up from the stairs. "What on earth was that?" Janet asked, clamping her hands across her ears.
"That," Jessica sighed, "is our so-called brother."
"It's Johnny Buck," Elizabeth put in. "He thinks he's singing Johnny's new song, 'Gotcha,' but he can't sing on key."
"'Gonna getcha, gona getcha . . .'" Mandy sang along. She shook her head sadly. "Too bad. It's such a great song. 'Gonna getcha, looked gonna getcha."
"Gotcha!" Janet yelled, suddenly jumping up.
Elizabeth smothered a grin. The other girls stared. Janet didn't often lose her composure, even over Johnny Buck.
When she saw everyone staring at her, Janet cleared her throat. "What I mean is, Steven's the one," she said, her voice now calm. "Oue guinea pig."

What will it take to make Jessica sick of cookies? Jessica's Cookie Disaster