Boo! Made You Jump! by Lauren Child

Charlie likes to make Lola jump, but Lola can never make Charlie jump. So Lola tries everything she can to scare Charlie. In the park, Lola and Lotta shout 'Boo!' - but it doesn't make Charlie jump. Then they dress up as scary ghosts, but that doesn't frighten Charlie or Marv at all. Will Lola manage to think of anything to make Charlie jump?