Sheldon's physicist joke about Feynman, Einstein and Schrödinger in a bar refers to their specific theories about reality. Feynman was known for his simple visual representations of complex mathematical expressions ("It appears we're inside a joke"); Einstein's theory of Special Relativity states that synchronous movement of objects depends on who is observing these movements ("But only to an observer who saw us walk in simultaneously"). The thought experiment of 'Schrödinger's cat' (mentioned on the show several times since The Tangerine Factor (2008)) describes a cat in a closed box with a vial of poison set to break at an unknown time; the only way to know for certain if the cat has died is by looking inside the box ("If someone is looking in the window, I'm leaving"). Sheldon's joke about Heisenberg being told he was going 85 miles per hour refers to the 'Heisenberg Uncertainty Principle', or the inability to measure both an object's location and speed in one observation ("Darn it, now I don't know where I am").
First time that Howard does a fair imitation of Stuart, apart from his well-known Bernadette impression.
When Sheldon and Amy begin their "Fun with Flags" webcast, you can see Amy mouthing along with Sheldon's introduction.
Title reference: the difficulty that Howard, Bernadette and Stuart experience when being separated from Halley while she is at daycare.
This episode was taped on March 28, 2017.