Just before I moved here to Tunisia, I worked at a steel factory in the UK. It was a friends 50th birthday and she thought that everyone had forgotten her. So, when it came time to leave at the end of the day, the boss made an excuse to keep her back for 10 minutes while everyone went outside to hide around her car. When she came out of the doors, her face was a picture!! Lizzy and I (Lizzy was another college) had snuck outside and saran wrapped her whole car up!! We stuck balloons inside it first so she had to unwrap it then get all the balloons out before she could get in it!!
I have to say, if you gotta blow up 100 balloons, get a bicycle pump, LoL!! My face hurt for two days!! LoL