Ba-Sing-A! 'Big Bang' Cast Drops Episode Song

Big Bang Theory fans got a special treat in last night's episode when cast members joined Howard (Simon Helberg) to perform an original song for his quarantined wife Bernadette and now the song is officially available for purchase!

PICS: TV and Movie Cast Reunions

If I Didn’t Have You (Bernadette's Song) -- now available on iTunes -- features Helberg singing lead with cast-mates Johnny Galecki (Leonard), Jim Parsons (Sheldon), Kaley Cuoco (Penny), Kunal Nayyar (Raj) and Mayim Bialik (Amy) providing backup vocals.

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The song -- which recognizes the show's support of the assistance program MusiCares -- was written by comedian, singer-songwriter and The Big Bang Theory recurring guest star Kate Micucci (who played Raj's ultra-shy ex-girlfriend Lucy), and her music partner Riki Lindhome, who both perform as the comedy folk duo Garfunkel and Oates.