The Big Bang Theory: 10 Best Characters Who Only Appeared In One Episode

Episode: "The Dead Hooker Juxtaposition" (Season 2, Episode 19)

"Best" doesn't always mean likeable, and that's certainly the case with Alicia (Valerie Azlynn). The attractive actress - who's more successful than Penny - moves into their apartment building and quickly proceeds to rub Penny the wrong way. She also uses her charms to exploit the lovestruck Leonard, Howard and Raj. Sheldon is immune, of course.

Things had been relatively smooth for the Big Bang Theory characters up to this point, and having an antagonist shake things up was a refreshing new angle. Valerie Azlynn plays Alicia as more of a snarky queen bee than an outright villain, and she deserves kudos for not falling into the stereotype trap. She definitely succeeds in making the audience dislike her and that is the hallmark of a memorable character.

Alicia's most unforgettable moment was her girl fight with Penny, which would've delighted many viewers and had them reaching for the rewind button. As impactful as she was, it's something of a relief that Alicia's wicked ways were restricted to just one episode.