Armin Shimerman (born November 5, 1949) is an American actor, voice actor and author. Shimerman is known for playing the Ferengi bartender Quark in the television series Star Trek: Deep Space Nine, Principal Snyder in Buffy the Vampire Slayer, Kramer's caddy Stan on Seinfeld, voicing Dr. Nefarious in the Ratchet & Clank series, and Andrew Ryan, one of the antagonists of BioShock. He played Dr. Potter in the 2011 movie adaptation of Ayn Rand's Atlas Shrugged.