Deer appear wandering in the player's home neighborhood following the installation of The Sims 3: Pets. A Sim can either 'watch', or 'shoo' the raccoon, although some Sims may be able to 'pet' them. Deer tend to hop instead of running. Watching and petting deer raises a Sim's hidden Wildlife skill.
Trivia
Male deer are always named 'Bambi', female deer are always 'Bambina'. However, on mouseover, they simply say "Deer".