There are in the most recent update being rolled out now - the first, which works in the Model S and Model X, turns your sat nav screen into a view of Mars. It won't actually take you to the Red Planet, but you can at least pretend you're driving across it.
To activate the hidden feature, enter "Mars" into the destination zip code field. The view pans accordingly as you drive, but make sure you keep your eyes on the road.
Lights, sound, action
The second Egg is for Model X owners only. Press the Tesla icon at the top of the in-car display for five seconds, and then when a password screen pops up enter "Holiday".
Exit your Model X, lock the doors, and the car starts playing music alongside its very own light show. Based on it's pretty impressive but make sure there's enough clearance for the doors to open and check there are no sleeping babies nearby.