An amazing, yet clever combination of the phrase "shit
face." Although still
mean, it provides for a less obvious or explicit way of making fun of someone who you
may not like.
"Oh, here comes Jillian. Look at her
face: it's
ugly and mean looking and her
face looks like she's going to take a shit whenever she looks our way. She's a regular shiffy."
or
"Oh, here comes Shiffy!"