Covered Up: Inverted, usually. Their covers tend to be awesome, even when the source material leaves something to be desired, and Alex has a habit of adding verses towards the end of the cover that are integrated so seamlessly you only notice if you're looking for it. They got hooked on it with their cover of LCD Soundsystem's "All My Friends," which is generally considered excellent and which a few (slightly ridiculous) fans consider better than the original. They managed to turn Gwen Stefani's (decent, but not wonderful) "What You Waiting For?" into a top-notch indie-rock stomper (and adding a bit of Billy Idol's "White Wedding" for good measure), and covered Britney Spears' (Britney Spears!) "Womanizer" and made it their own (with a dash of their own "Shopping for Blood" for good measure). Their covers of other artists (e.g. the one they did of David Bowie's "Sound and Vision") are more faithful, but still recognizably them.
They also covered Blondie's "Call Me," occasionally with Elly Jackson. Once again, it is very different, and very 'them.'
Ear Worm: Take me out, The Fallen, Do You Want To, Ulysses...
Heck, pretty much all of their songs will have something you remember about them.
Sophomore Slump: You Could Have It So Much Better, while still quite good, is considered to be considerably worse than both Franz Ferdinand and Tonight. Most critics attribute this to the fact that they sort of rushed it (releasing it about eighteen months after their debut) in order to prove that they weren't just a flash in the pan, while they could take their sweet time on their debut and Tonight.