Hofstadter Isotope — [s2e20] The

The story kicks off when the guys visit the comic book store. While there, Stuart Bloom, the store owner, uses his artistic talent to sketch Penny and charm her into a date. Leonard is devastated and jealous, leading to two parallel storylines:

This episode marks Stuart's first appearance. Unlike his later seasons where he is portrayed as increasingly pathetic and sickly, he is initially shown as confident, talented, and a genuine romantic rival for Leonard. [S2E20] The Hofstadter Isotope

One of the most discussed moments among fans is Penny's invitation for "coffee," which Stuart famously takes literally, much to Penny's amusement. The story kicks off when the guys visit the comic book store