Melissa Rauch as Bernadette Rostenkowski-Wolowitz
Bernadette was first introduced in Season 3 when Penny offered to set her up with Howard. Although there wasn't an immediate connection, the pair ended up typing the knot several seasons later. Bernadette quickly became a regular on the show, serving as Penny's first female companion.
Lauren Lapkus as Denise
Lauren Lapkus played Denise, the assistant manager at Stuart's comic book store. At first, Sheldon wasn't fond of her, but he warmed up to her after learning that she was genuinely interested in comics. Denise and Stuart formed a relationship, eventually moving in together toward the end of the series.