兔崽子 is a rough insult, often used by older people scolding younger ones. It can range from genuinely angry to gruffly affectionate depending on tone and context. Avoid in polite company.
history
Originally 兔崽子 literally means 'baby rabbit.' Rabbits were associated with promiscuity in traditional Chinese culture, so 'offspring of a rabbit' became an insult implying illegitimacy.
