When driving a Tesla, you engage the lane assist/cruise control function by pressing a button on the right stalk, twice. 

If you're not sure it engaged, or you can't remember how many times to press it, and you press the button four times, you engage an "easter egg" known as the rainbow road. 

When engaged deliberately, it's a nice collection of in-jokes. I did not engage it deliberately. I engaged it accidentally, at night, on the highway, in an unfamiliar city, surrounded by traffic in narrow lanes I was hoping lane assist might help me with. 

First, the sound of my audiobook was drowned out by a full-volume rendition of "don't fear the reaper." I had to look away from the road to scramble for the pause button, which stopped my audiobook but not the music. As I was turning the volume down, the music was joined by a loud metallic banging noise, which a voice soon identified as a cowbell, not a car accident. 

As all this is happening, the navigation screen in the car began flashing rainbow lights, demanding that I try to figure out how to stop it rather than watching the road. Again, I am moving full speed in highway traffic while trying to troubleshoot these sudden noises and lights. 

The way to turn this 'easter egg' off, is to hit the brakes.

The brakes on a moving vehicle should be engaged because it is safe and necessary to do so. No driver should *ever* be required to suddenly decelerate in traffic, simply in order to put a stop to a 'joke' or a 'prank.' This easter egg (and any similar features I haven't discovered yet) should be disabled immediately.

It should not be possible to engage distracting and pointless entertainment while the car is in motion. At the very least, it should be IMMEDIATELY obvious how to turn such 'features' off, without disturbing the flow of traffic.