Complex sentence: In the episode "Seventeen Candles", Chuck gives Blair a diamond necklace for her birthday; and because of Blair's love of Audrey Hepburn, there is a misconception that the diamond necklace is from Tiffany's.
Split into simpler sentences: In the episode "Seventeen Candles" Chuck gives Blair a diamond necklace for her birthday. Because of Blair's love of Audrey Hepburn, there is a misconception that the diamond necklace is from Tiffany's.