Pet Shop Boys' wry, ultra-literate synth-pop has rubbed off widely. Some artists pick up on their impeccable poise—the spoken-word parts of Lady Gaga's “Alejandro” are pure PSB. Others, like Robyn, flock to their cool, controlled, and hook-heavy electro-disco. And then there's Robbie Williams, whose tongue-in-cheek “Rock DJ” brims with an arch wit the duo surely appreciate.