Although the Bing-Bong Bell was mainly used by Queen Delightful, a few other characters have used it: Starchbottom (through much hesitation) used it in "The Fairest in the Land" because the queen became a troll. In "Sleepytime", Sir Yipsalot used it to seek the help of The 7D because a sleeping spell was cast over the kingdom; only Sleepy arrived at the castle (he was already sleeping when the spell was cast) and together they managed to break the spell. (Sir Yipsalot had to press a button installed on the wall to have the rope come to him since he's a dog.)
The origin of the Bing-Bong Bell is explained in the episode "Bing Bong Beans". It's a set of three bells housed inside a tower next to a home of a giant in the sky above Jollywood in the Kingdom of the Clouds. Delightful and The 7D believe the bell malfunctioned because it continues to ring even though it's never been called upon. So the dwarfs travel to the Kingdom of the Clouds by way of the Bing Bong Beanstalk to have it fixed.