I think it was season 1, episode 8.
The episode in which Penny is practicing mixology in her kitchen is the 8th episode of Season 1, The Grasshopper Experiment. It is after the first time Penny mixes a grasshopper for Raj that she hears Raj speak for the first time.
Penny tells Leonard that he's "destroyed her ability to tolerate idiots" in The Lunar Excitation (Season 3, Episode 23).
"The Bath Item Gift Hypothesis" Season 2, Episode 11
That's the season 2 Christmas episode, and the first Big Bang Theory Christmas episode. The episode number is 11 and the name is "The Bath Item Gift Hypothesis"
episode 8, season 3, 'The Adhesive Duck Deficiency'
Gucci
Leonard has strong feelings for Penny in the very first episode, and their first date is in the third episode -- "Fuzzy Boots Corollary." Their relationship is on-again, off-again for every season afterwards.
Penny becomes addicted to the online game Age of Conan. This all takes place in season 2, episode 3: The Barbarian Sublimation.
The game was Age of Conan; however, Sheldon showed her the game, not Howard.
Penny - The Big Bang Theory - was created in 2007.
Adhesive ducks episode.......my favorite the guys except Sheldon go to the desert to watch a meteor shower and get stoned on pot cookies....lol. Sooooo funny
"The Bath Item Gift Hypothesis" -- an event I consider one of the funniest moments in the history of all television!