"Karan has always considered Kajol as his lucky mascot. So for 'Student Of The Year', he wanted her to do a special appearance and she readily agreed," a source told PTI.
Johar, who made his directorial debut with 'Kuch Kuch Hota Hai', had Kajol and Shah Rukh Khan in the lead. His following releases 'Kabhi Khushi Kabhi Gham', 'My name is Khan' and 'We are Family', too, had Kajol in the lead.
In his films as a producer, like 'Kal Ho Na Ho', and 'Kabhi Alvida Na Kehna', Kajol appeared briefly in one song each from both the movies.
"For this film ('Student of the Year'), she has already shot her part," the source said.
However, whether Shah Rukh is also doing a cameo in the film is yet to be known.
Directed by Johar, 'Student Of The Year' is a romantic-comedy. The film marks the debut of Alia Bhatt, daughter of filmmaker Mahesh Bhatt, Varun Dhawan, younger son of David Dhawan, and newcomer Siddharth Malhotra.
The film has been produced by Johar and Shah Rukh under the banner of Dharma Productions and Red Chillies Entertainment.