On a recent episode of MBC "Younha's Starry Night," f(x) members were asked if they would like to perform with a member from a different singing group.

Krystal expressed, "I want to try something with my sister (Jessica)," and "During SM concerts we do a lot of collaborations and they're really fun. Performing with my sister on stage has been strange yet fun." 

f(x) member Luna chose SHINee's Onew saying, "Onew and I have good chemistry so I would like to try something more formal."