There is an Easter Egg in Notes. If you can get a magnified view of the the icon for the Notes app, you will see that the scribbling shown on the notepad is a tribute to the ancient but famous "The Crazy Ones" Apple TV ad from the late nineties – part of the "Think Different" ad campaign. The text reads:
"Here’s to the crazy ones.
The misfits. The rebels.
The round pegs in the square holes.
The ones who see things different.
They’re not fond of rules,
and they have no respect for the status quo."
Hat tip MacObserver