This is the tenth of 12 appearances Kitty Sullivan makes in the series as Sue Ellen. The character appears first in The Tycoons (1964), but is played by Susan Tyrrell.
This is the second of two appearances Doris Belack makes in the series, each time appearing as the teacher Miss Grey.
Patty sympathetically calls Richard 'Poor Richard', an allusion to the eponymous character Benjamin Franklin created for his "Poor Richard's Almanac."
The title plays on allusions to evolutionary concepts furthered by two 19th century biologists: Charles Darwin, whose work is often associated with the suggestion that mankind evolved from apes, and Gregor Mendel (1822-1884), whose experiments with peas is to this day studied and sometimes replicated in high school biology classes, such as the one Mr. Noble teaches.