by algotruneman - uploaded on October 14, 2016, 8:57 pm
I believe it is standard practice to use a margin which is puffed out when expressing a cartoon character's thought instead of speech.
I recommend Nick Piekos' recommendations: http://www.blambot.com/articles_grammar.shtml
This clipart is a remix from:
Thought Bubble
by @NicholasJudy456