This is a copy of a french movie Dîner de cons, Le (1998). Also known as "The Dinner Game" (English title). Someone says that it has been copied from dinner for schmucks which is absolutely wrong as this released in 2007.
Ranvir Shorey and Vinay Pathak are best friends in real life too, and worked in several films together.
In the beginning of the movie, the first dinner guest is Sharat Kataria, who had also written the dialogues of the film. Also, he is the writer of hit films like Dum Laga Ke Haisha, Fan and Sui Dhaga.
Hollywood later made its own adaptation from the original French film. It was made as "Dinner For Schmucks".
Director/Producer Anurag Kashyap was greatly impressed with Ranvir Shorey's performance while the movie was being edited.