Season 10, Episode 19 - The Collaboration Fluctuation
Aired March 30, 2017
When Penny and Raj start spending more time together now that Raj has moved into the apartment, Leonard starts to feel like a third wheel.
Meanwhile, Sheldon's interest in Amy's work leads them to collaborate, but they soon find they can only work well together when they're at each other's throats.
Season 11, Episode 5 - The Collaboration Contamination
Aired October 23, 2017
When Howard and Amy work together on a project, Sheldon and Raj struggle with feelings of jealousy and loneliness. Meanwhile, Penny and Leonard find a new way of dealing with Sheldon from an unlikely source.