a person (usually a girl) who stays indoors in bed/watching tv and on the sofa during the day and only goes out in evening/night time and only if necessary! Its normal for a catbat person to be somewhat lazy or fatigued during the day, but their energy levels gradually rises when darkness approaches.
me: im thinking of asking that girl i bagged last week to join us at the beach
them: ah you mean Sally the catbat? good luck with that, she's probably home in bed right now