In The Pilot Kevin says he has known Paul since Paul was 36 hours old. Here we learn Kevin is four days younger than Paul.
Paul's bar mitzvah occurs on Saturday, March 18, 1969, which is also Kevin's birthday. March 18, 1969 was a Tuesday.
Kevin said he was jealous of Paul. The correct term would be envious.
After Kevin's family sings him happy birthday, Karen gives him a gift of a poem. When she stands up to read it, directly above her is a hanging boom mic which is quickly corrected.