1) Katy Perry - Last Friday Night (T.G.I.F.)
It's been a good year for Katy Perry, with two No 1 hits in the US and two Top 10 singles in the UK. One such chart-topper is the infectious hit Last Friday Night (T.G.I.F.), which spawned one of her most memorable videos to date.
Inspired by a night of partying and streaking with her friends (oh, Katy), as well as the high-school movies she grew up watching in the 1980s, the video follows her geeky alter-ego Kathy Beth Terry as she throws the party of a lifetime with the help of a few friends.
Rebecca Black - of Friday fame - provides the geeky Kathy Beth with a glamorous makeover, while Hanson and Kenny G team up to provide the music. And if that wasn't enough, Artie and Blaine from Glee also make an appearance. Nobody can bring out the mid-level celebrities quite like Katy Perry!