Pop star Fergie celebrated her 42nd birthday on Monday where she was serenaded by her husband Josh Duhamel and her son Axl. On Instagram, Duhamel posted a video of himself and Axl along with a room full of family and friends singing the birthday song to Fergie Ferg. The "Fergalicious" singer also celebrated with a unicorn cake covered in flowers made from icing and a huge golden horn. Fergie shared a picture of the cake on her Instagram and in the caption she included the hashtags urbanunicorn and thelastunicorn.