The technical consultant, David Saltzberg, appears. He was the first person on the left that Howard passed when he entered the dining room introducing Bernadette as his girlfriend to everyone. (Look for the guy in the brown sweater vest at the first table).
This marks the first time Bernadette is in Leonard and Sheldon's apartment. Howard introduces her as his girlfriend.
Howard says he practically invented using fancy lab equipment to seduce women. An example of Howard using this technique is letting Sara Rue drive with the Mars rover in episode 2.8, The Lizard-Spock Expansion (2008), (into a ditch, no less).
Title reference: Penny's suggestion that Sheldon should treat teaching her physics as an experiment. Sheldon subsequently names the experiment "The Gorilla Project," after Koko the gorilla who learned sign language.
When Sheldon is going through the algebra on the white board with Penny, he is trying to prove to her that objects fall with a constant acceleration of 9.81 meters per second squared in Earth's gravity, via Newton's second law of motion (the equation F = ma).