‘Shake It’ is one of the Battle Emotes options that you can customise your Ninjala character with; the emote is performed at set stages of a battle.
By going into the Closet and then the Battle Emotes menu, you can pick Shake It as the move that your ninja performs at the start of a battle, when you win, or when if you lose.
‘Shake It’ Official Description
“Get jiggy with your bad self. Increasingly addictive each time you dance.”
‘Shake It’ Animation
As far as Battle Emotes go, Shake It is one of the more rhythmic options, seeing your Ninjala character perform a little dance while musical notes fly around.
It’s a joyful option to pick, so it’s likely designed for victories or perhaps at the start of a battle.