Complex sentence: He also also designed hats worn by Lady Gaga, the most notable being a telephone-shaped headpiece with removable handset that the singer wore on her appearance on Friday Night with Jonathan Ross in 2010.
Split into simpler sentences: He also also designed hats worn by Lady Gaga. The most notable of his designs was a telephone-shaped headpiece with removable handset worn on her appearance on Friday Night with Jonathan Ross in 2010.