About the remote "not"
It is an idiomatic nonstandard usage especially in informal, humorous contexts:
Not:
(humorous, informal) used to emphasize the opposite of a statement.
Well, that sounds like a fun evening—not!
(oxfordlearnersdictionaries.com)
It usage dates back to the beginning of the 20th century but was made popular a few decades ago:
Not:
As an interjection to negate what was said before or reveal it as sarcasm, it is attested by 1900, popularized 1989 by "Wayne's World" sketches on "Saturday Night Live" TV show.
(Etymonline)
From: American Speech Vol. 68, No. 2 (Summer, 1993), pp. 213 Published by: Duke University Press.
(jstor.org)