I've drawn Mark and Abby together a lot over the last five years, both through the book itself and commission requests. It's always a challenge to find something different. It's also a challenge to find a way to 
make them work together. The cartoony nature of the characters and the body types and proportions don't always mesh well together. You have to work to make sure they belong in the same universe. I think I've mentioned it before, but any scene where Mark and Abby are drinking is work to make both their hands hold the same size glass.
When asked to draw this, I took advantage of having studio time and pads of tracing paper and worked with the pose. I was able to do one of those hugging-from-behind poses. I further cheated just a little by making the two of them flying so their feet didn't have to be on the same plane.
I really like this image, and I think you'll be seeing it again somewhere…