When does impaginary play start?

[set81616]

I swear DS (15 months today) was pretending to eat this weekend. He would put his drum stick in his stacking cup and then in his mouth and start chewing (after pulling the drum stick back out). It was so funny. He did this for a while and when I asked him if he was eating something yummy he just looked at me and smiled and started chewing again.
Shannon

[LarsMal]

DS is 16 months old and he is doing something very similar. He has a stuffed caterpillar to go with his hungry caterpillar book and I made a chewing sound one time when I was reading it. Now every time he picks the book up and opens it (or plays with the caterpillar), he makes the pretend eating sound. He does it while looking at the food, too, so I know he's "pretend eating". Not sure if it's imaginary or just copying me, but it's still cute!

[BeachBum]

At about 13 /14 months my son would "feed" his stuffed animals, make squirting noises with the hose, and use a watering can with noises and shake it in each of the plants. At 15 mo he would make pretend toast, and feed it to me or a stuffed animal, wash dishes (making sounds for water at his play kitchen), make his stuffed animals kiss etc.
I just assumed it was pretty normal.