I was going to mention about An earth pony's pegasus girlfriend (0:39). Plus, Princess Cadance (Alicorn) and Shining Armor (Unicorn).
May include Rarity parents if Rarity's dad has a horn (plus he has a football cutiemark, which means he could be an earth pony unless he is a unicorn quarterback).
P.S- I don't think Lars has some love for MLP.