[s3e9] The Vengeance Formulation -

The "piece" you are referring to from episode " The Vengeance Formulation " (Season 3, Episode 9) is likely the song Howard Wolowitz performs for Bernadette at the Cheesecake Factory.

In this same episode, Howard also has a notable fantasy "piece" or sequence involving (playing herself as her Battlestar Galactica character, Starbuck) while he is in a bathtub, where she helps him realize his true feelings for Bernadette. Katee Sackhoff - The Big Bang Theory Wiki | Fandom [S3E9] The Vengeance Formulation

: While Bernadette is touched by the gesture, she initially rejects his subsequent marriage proposal because they had only been on three dates. However, they agree to continue dating. The "piece" you are referring to from episode

: To win Bernadette back after she stops returning his calls, Howard performs a grand, albeit awkward, musical apology in the middle of her workplace. However, they agree to continue dating

: Howard sings a parody version of the 1960 hit " Bernadette " by The Four Tops .