Flitter and Cloudchaser from Hurricane Fluttershy: Season 2, episode 22 
They were a bit mean laughing at Fluttershy but I don't think think they meant it.
I really want to see more of these two. Especially such that we can see Flitter's Cutie Mark unblured and unobscured so we can actually see what it looks like. I had to make a guess based on what I could find out from the wiki "three dragonflies". I vectored my own Cutie Mark for flitter.
SVG available here: [link]
Cloudchaser & Flitter © Hasbro
My Little Pony: Friendship is Magic © Hasbro