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.
Leonard: Hi. I'm Leonard. You are beautiful. You pop, sparkle and buzz electric. I'm going to pick you up at eight, show you a night you will never forget. Raj: Where are we going?
[Raj whispers in Wolowitz's ear] Penny: What did he say? Wolowitz: He compared Sheldon to a disposable feminine cleansing product one might use on a summer's eve. Penny: Yeah, and the bag it came in