I used Komika Bubbles Font (http://www.fontspace.com/apostrophic-lab/komika-bubbles).
There are 20 conversation or thought bubbles in this font.  I emailed David a PPT file with an "alphabet" image and a slide of vector images for each bubble in the font--I also posted this image to the Komika Bubbles page.  
I've attempted to share the PPT presentation here: 
https://drive.google.com/drive/folders/0B8RHT2zAEn4ybDdIWW9UeFJKUTg?usp=sharing For reference, the website and license information about the font is included on its own slide at the end of the PPT file.
I slapped together a little interaction that uses the icons as buttons.  There's obviously a lot of directions you can take these little assets!  Fun challenge, thank you David!
The demo is posted here: 
http://elearning-examples.s3.amazonaws.com/Weekly-Challenge/165-FontIcons/IevaSwanson/story_html5.html