The film helmed by 'Go Goa Gone' fame director duo Raj Nidimoru and Krishna DK, also stars Saif Ali Khan, Govinda and Ileana D'Cruz.
In 'Happy Ending', the 30-year-old actress, whose last release was 'Yeh Jawaani Hai Deewani' in 2013, plays an America-returned girl obsessed with Saif's character.
"I am playing a crazy woman named Bisakha and she is an ABCD - American-born confused desi. She is obsessive about Saif in the film. 'Happy Ending' is a spoof on our film industry and on all the romantic comedies. But it is a healthy spoof," Kalki said.
When asked how she bagged a role in a comedy, the actress, who has mostly starred in films with serious content like 'Dev D', 'That Girl in Yellow Boots' and 'Shanghai', said, "I guess I have a good comic timing and people have seen that in 'YJHD'... so that must have worked for me."
Kalki said although she did not have many scenes with Govinda in the film, she was amazed to see how he would deliver the funny dialogues with ease.
"With Govinda ji I don't have many scenes because our tracks are different. But I have seen few scenes of him, it is just superb especially the comic timing. He delivers funny dialogues with a dead pan face which is commendable," said the actress, who has grown up watching hit Govinda songs.
Besides 'Happy Ending', which will hit theatres on November 21, Kalki is also awaiting the release of Shonali Bose's 'Margarita, with a Straw', in which her character is inspired by the director's own cousin who has cerebral palsy.
"I was scared to play the role. I have done a lot of hard work in this film, spent a lot of time with her and I got to know about her. I also met with a physiotherapist to know the body language," she said.
The film premiered at Toronto International Film Festival and London Film Festival.
Kalki will also be seen alongside Richa Chadha in 'Jiah aur Jiah', which is a film about the bond between two girls.
"In the Hindi film industry we mostly have films on boys bonding. There hasn't been many films about female bonding.
But 'Jiah aur Jiah' is a film which will show the girls bonding.
"I am playing a free spirited Punjabi character and Richa is just opposite of me in the film. We both go for a trip. The film is about enjoying life," Kalki said.
The actress will soon begin shooting her next two films - Anu Menon's 'Waiting' with Naseeruddin Shah and Soni Razdan's directorial venture 'Love Affair' opposite Arjun Rampal and Gulshan Devaiah.