It's not a Deer Knight; they take five minutes to hatch. (I should know; I have seven.)
A trick I use for finding out what's in the egg before it hatches.... go to the pets tab in your backpack and mouse over the egg. If the unhatched pet gets an item card, the type of item card should show when you mouse over. Info about the item card tells you what the pet will be when it hatches.
Miranda Nightsinger, Promethean Necromancer Scarlet Windhammer, Magus Pyromancer