Serebii is the second daughter of Monster X and Biollante, and the little sister of Celebi
Serebii is basically a Celebi wearing a diaper and has a flower bib in its mouth.
In "Birth of Serebii," Biollante gave birth to Serebii. For the sake of ease, the family called her Serebii. She can only say "Goo."In the end of one of the Kaiju Kritics Fan Mail Fest, Celebi is teaching Serebii on using Instant Transmission, Time Travel, and the Enterprise's Teleporter. My Little Goji: Epilouge she says "goo" and "Sorry sis, I thought I could milk it a little longer." And "Engage clothes!". It can be assumed that Celebi will make Serebii one of her loyal lackeys.