Most Logical Answer Yet
from: Rob Theakston [email@example.com]
to: Y.P.R. [firstname.lastname@example.org]
subject: Don't know if anyone answered yet.
The 'P' in Alex P. Keaton stands for Peace. Elise and Steven were both hippies in the sixties. There was one episode where they had a flashback to when Alex was a baby and showed how Alex got his middle name.