Bangalore: Jury member for the last two editions of Indian Idol, singer Sonu Nigam will be back on Indian Idol in the episode to be aired on 17 August 2007 as a special guest.Sonu is to make an impromptu appearance, as the surprise element for the show, according to Miditech president and Indian Idol 3 executive producer Niret Alva. Also on the agenda are performances by jury member and singer Alisha Chinai. Fellow judges Anu Malik and Udit Narayan could also hum a few lines on the show, according to Alva, as could Sonu. This is Sonu`s first appearance after his return from the US where his wife recently delivered a baby. Last week`s special guest was Bollywood actor Anil Kapoor.