Slip (one) a Mickey (Finn) spoken language verb phrase
To put in one's drink a drug that can cause them to be unconscious or incapacitated.
The kidnaper slipped Jane a Mickey Finn and took her to an abandoned house.
A girl like you shoudn't go to bars alone. Because some with a bad will can slip you a Mickey Finn.
People have still been looking for the one who dared to slip the princess a Mickey Finn.
Jone saw someone slip Rose a Mickey Finn, but he couldn't see his face.
It's mostly used in the past tense.