妹子 [mèi zi] = 妹纸 [mèi zhǐ] n.
Literally “younger sister”, this term is often used by a guy to refer to a girl younger than him. 妹纸 [mèi zhǐ] is a phonetic deviation that mimic the Northeastern accent for comic effects.
On a Winter day, a girl got a fever and her face was all red. She went to the clinic. The doctor came in and put his hand on her forehead. 30 seconds later he switched to the other hand. And then, this crazy doctor said, “So warm.”