During the first encounter of Simon Phillips and Walter Bishop, Simon recites the random thoughts that Walter thinks. One of them is the mathematical definition of the Mandelbrot Set on the imaginary plane: "Z-two equals Z-one square plus C"
Concentrate and ask again is one of the 20 possible answers provided by the Mattel "fortune-telling" novelty toy the Magic 8-Ball.
The glyphs for this episode spell out: HATCH
During the episode's opening scene, Nina is examining William Bell's old office. Among the books in office is a book by early childhood expert Dr. Benjamin Spock. Possibly a clever nod to Leonard Nimoy's iconic Star Trek character portrayal: "Spock".