Cas had been glued to his phone screen all day. Dean really wanted to know, but wasn't sure how to ask, what the angel was doing.
In the end it was Sam that asked, "Cas? What are you doing?"
"Helping a small green creature eat large red candy," Cas said. The Winchesters looked at each other and decided not to ask.
I'm giving up on saying where I got the prompt from, it's far too hard to keep them all straight in my mind so... From now on I won't say :) I hope no one minds