YA Fantasy. A character named Quimby has his head inflated like a ballon and floats out of a nearby window.

[T.R.W]

I read this book around 2010 or so. I believe it featured a brother sister duo that find themselves in this secret magical world of mystical creatures. There is an academy or boarding school they end up attending even though I don’t remember them having any sort of special ability. Most importantly, a small goblin (I’m thinking rumplestiltskin-esque) that gets cursed or something and his head begins to inflate before he goes whooshing out of a window shouting “Quimby needs help!”.

I distinctly remember that later on the two main characters end up falling through the sky somehow and land on top of Quimby’s head as he is still free floating through the clouds. By this time he has calmed down and starts spouting “deep” hilariously philosophical phrases while the children sit atop his head wondering how the heck they’re going to get out of this situation.

[Lobstergirl, au gratin]

Can you give us an update on your other thread here?

https://www.goodreads.com/topic/show/...

[Rainbowheart]

Are the brother and sister teenagers or younger children?