Gianiji was celebrating his 75th Birthday and all his friends were invited.
To surprise the Giani, his friends arrange for a beautiful call-girl to seduce the old man. After the party, all the old guys wait outside his bedroom and send the girl inside. Very soon they hear the girl moaning "Giani, Giani". This goes on for about half-an- hour, after which the Giani comes out looking sweaty and half-dead. His friends are amazed that even at this age he could make a young girl moan for more, and ask him the secret of his tandrusti.
Then Giani Zail Singh, takes a deep breath and says "Arrey Yaaro, who 'Giani Giani' nahi bol rahi thi, woh to 'Gaya nahin gaya nahin' bol rahi thi"