See https://twitter.com/xcv58/status/1248311559949914112.

The main menu bar has an animation when you mouse over the "bell" or "messages" icons: they highlight and move a little bit.

In Chrome (at least, but not Safari), if you put your cursor on the very bottom of the element, it will rapidly bounce up and down.

These "bounce" animations are unusual in modern Phabricator and a possible fix is to simply remove them, but they're kind of nice.