I never seen the penitentiary
I've been shook since I seen the Haiti Kid in Penitentiary 3

from R.A. The Rugged Man – Midnight Thud Lyrics on Rap Genius

Meaning

The 1987 film Penitentiary III features a ferocious little person named (wait for it) Midnight Thud, whom the sadistic guards would throw in your cell to kick your ass.

Thud was portrayed by midget wrestler The Haiti Kid. Does the whole song make a little more sense now?

“Never seeing the penitentiary” is a double entendre here:

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