On The Big Bang Theory Season 8 Episode 22, Leonard gives a graduation speech via Skype with the help of Penny, and sports cap and gown that doesn't exactly fit.
On The Big Bang Theory Season 8 Episode 20, Penny and Leonard argue over whether or not Penny should take an audtion for a film while on a podcast with Will Wheaton.
On The Big Bang Theory Season 8 Episode 18, the gang gathers together for one final dinner to honor Mrs. Wolowitz, eating the last food she ever prepared.
Sheldon: I'll have a diet Coke. Penny: Can you please order a cocktail? I need to practice mixing drinks. Sheldon: Fine... I'll have a virgin Cuba Libre. Penny: That's... rum and Coke without the rum. Sheldon: Yes, and would you make it diet?