Kevin Sussman says it took just one unscripted moment to permanently reshape Stuart Bloom on The Big Bang Theory. Introduced in Season 2 as a fairly normal, soft-spoken comic book store owner, Stuart slowly transformed into one of the show’s most painfully unlucky characters — and that shift began with a single improvised line.
Speaking at the 2021 Paris Manga & Sci-Fi Show, Sussman revealed that during Season 3’s “The Guitarist Amplification,” he quietly muttered “I love you” under his breath as Penny exited a scene — a line never written into the script. The moment caught the writers’ attention and helped define Stuart’s increasingly desperate, regressive arc.
What started as a spontaneous joke ultimately shaped Stuart’s identity for the rest of the series. Sussman will reprise the role in the upcoming HBO Max spin-off Stuart Fails to Save the Universe, set to premiere in 2026.
