A couple of days ago, I gave my husband rare control of the DVR decided to catch up on some backlogged hours of Doctor Who, and caught a particularly awesome (albeit atypically structured) episode called “Blink.” The plotline centered on a young woman named Sally Sparrow, who had to solve the mystery of her best friend’s disappearance with help from the Doctor (who happened to be trapped in 1969 and transmitting messages through DVD “Easter eggs”). The episode was riveting — filled with romance and thrills and terrifying stone-angel statues — and hinged entirely on the star-making performance of the actress playing Sally. Thanks to the power of IMDb, I found her name (Carey Mulligan, pictured) and a list of her credits within seconds of shutting off my TV, then added her 2005 miniseries Bleak House to my Netflix queue. (I’d been meaning to watch it anyhow, and now I’ve got the perfect excuse.)

All this got me wondering: Who was the last unfamiliar actor you became obsessed with thanks to a TV guest spot? And did your fascination continue after you’d seen them in a followup role? All must be revealed, PopWatchers!