What is the origin of the bubble during sleep trope?


A common trope across various anime and manga is the [snot bubble
trope](http://tvtropes.org/pmwiki/pmwiki.php/Main/SnotBubble). I've put an
example below:

[![](https://i.stack.imgur.com/kqEmO.jpg)](https://i.stack.imgur.com/kqEmO.jpg)

I can gather what it signifies from the [TV Tropes
description](http://tvtropes.org/pmwiki/pmwiki.php/Main/SnotBubble), but
what's the origin of this? Does anybody know where it was first used, or where
the inspiration came from?




The origin is, perhaps surprisingly, real life! This does occur among
[children in Japan](https://www.flickr.com/photos/altus/1515466596) and [in
other countries as well](http://jemblankz-
monstervikings.blogspot.jp/2011/06/funny-snot-bubble.html).

![enter image description here](https://i.stack.imgur.com/dvp2q.jpg)

![enter image description here](https://i.stack.imgur.com/zqk4c.jpg)




The origin is, perhaps surprisingly, real life! This does occur among
[children in Japan](https://www.flickr.com/photos/altus/1515466596) and [in
other countries as well](http://jemblankz-
monstervikings.blogspot.jp/2011/06/funny-snot-bubble.html).

![enter image description here](https://i.stack.imgur.com/dvp2q.jpg)

![enter image description here](https://i.stack.imgur.com/zqk4c.jpg)

