Side chick
A side chick is a girl that is being dated by a guy who is in a serious relationship with someone else (main chick).
The girl he was with is his side chick.
Tikoloshe
In Zulu/Xhosa mythology, Tikoloshe, Tokoloshe, Tokolotshe, De'Avion or Hili is a dwarf-like water sprite. It is considered a mischievous and evil spirit that can become invisible by drinking water or swallowing a stone. Tokoloshes are called upon by malevolent people to cause trouble for others.
*My child misbehaves*
Me: If you don't behave, I will call the tikoloshe to beat you.