Chibiusa pouted and threw temper tantrums. Why? Because Neo Queen Serenity and King Endymion were putting Chibi Chibi to sleep, Chibiusa was being impatient because they were paying attention to Chibi Chibi and not her. And Chibi Chibi is only a newborn, so she wouldn't understand. You're the oldest child of Neo Queen Serenity and King Endymion, and you were just cleaning up Chibi Chibi's mess in the playroom until Chibiusa stormed in

Chibiusa: WHY IS EVERYONE PAYING ATTENTION TO HER, BUT NOT ME!? I'M THEIR DAUGHTER