Sheppard has played some memorable villains

Even before his time as a main cast member on "Supernatural," you had likely seen Mark A. Sheppard in action, probably in some type of villainous role. One of his earliest television gigs was actually on The Brit played the pyrokinetic monster-of-the-week villain Cecil L'Ively in the Season 1 episode "Fire.

" From there, he bounced around between different shows, guesting as characters like Badger on Joss Whedon's "Firefly," the Ring Leader on "Chuck," and Canton Everett Delaware III on "Doctor Who" (more on that one later).

Before he played Crowley, Sheppard's most famous roles were the Season 5 villain Ivan Erwich on "24," recurring attorney Romo Lampkin on "Battlestar Galactica," and insurance investigator James Sterling on "Leverage.

" Additionally, he appeared as con artist Curtis Hagan on "White Collar" and the cynical Warehouse Regent Benedict Valda on "Warehouse 13," proving himself to be a formidable television staple. Of course, that all ended when Sheppard got promoted to a series regular on "Supernatural."

Upon leaving Crowley behind, Sheppard went back to being a guest star with a turn in a Season 1 episode of the "MacGuyver" reboot, but that was just a one-time thing.

At that point, Sheppard had proven himself to be series regular (or, at the very least, recurring character) material, and he wasn't going to look back.

Sheppard wasn't happy with how Crowley's story ended

Mark A. Sheppard was less than thrilled about how his run on "Supernatural" came to an end.

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