Answer:
What is filled with air and sometimes a gas, tied to a string and often seen on your birthday?
Watches students at the prom to make sure there's no funny business.
What goes through a door but never goes in and never comes out?
I have joy in bringing two together, but darning my existence! My life hangs by a thread, filled with ups, downs and resistance!
What can be seen but not touched?
What is full of holes but still holds water