那些恶作剧者在老师的椅子上放了个会发出声音的垫子。

The ___pranksters put a whoopee cushion on the teacher's chair.

那些恶作剧者在校园里放了一只会动的假蜘蛛，把学生们吓得不轻。

The ___pranksters placed a robotic fake spider on campus, giving students quite a scare.