This was a commission for SecretTacoNinja (on DA: http://secrettaconinja.deviantart.com/) of Gordon Freeman and Alyx Vance as ponies.
The description I was given was that Alyx should be a pegasus and Gordon an earth pony. And since they kill aliens and zombies together but they're also kind of a couple, she requested it to be "kinda cutesey but then they're also covered in zombie blood and guts". The end result is less gory than how the description sounds, IMO, but I was worried about overdoing it.
Oh, and my experience with Half-Life is pretty much limited to "Freeman's Mind" and "Full-Life Consequences", so hopefully I did it justice--thank god it has a wiki =P