One year, we got a tank of compressed air and a bunch of balloons and stayed after work and literally filled his office with balloons. Floor to almost ceiling. Not only was it hilarious, but popping the balloons the next day was a lot of fun, and clean-up wasn’t too hard. You absolutely need compressed air for this, and even then it took an hour or so to do.
These days, I guess it’d be seen as environmentally wasteful; balloons aren’t recyclable, I think. Plus, it only works if she has dedicated office with a door. If it’s still an “office” but shared with another person, you could still get their permission; maybe they’d agree to hotel in a conference room until the balloons are popped.
guyrocket