It may also happen randomly during the day or at night when they take off running for no reason or attack your shoelaces or (insert random object here) so fiercely you dare not move or you will be ripped to shreds.
Person B: "Yeah, you gotta watch out for her. She can get into kitty mode pretty quick."
Person 1- "Dude I'm sooo hungover!"
Person 2- "Bro, I know. I'm gonna kittymode alllll mothatfuckin day."