balloon knot

balloon goes up

Something exciting, risky, or troublesome begins.

get one's knickers in a knot

Synonym of get one's knickers in a twist.

get one's shorts in a knot

Synonym of get one's knickers in a twist.

tie the knot

To marry, wed, get married.

trial balloon

An idea, suggestion, or prospective action, product, etc., offered to an audience or group in order to test whether it generates acceptance or interest.