Erin was at the company picnic at the end of season 5 and should know who Holly is because she and Michael did a memorable skit in which they revealed the Buffalo branch was being closed.
Angela says that the state senator deserves congratulations for getting a bill passed to implement parking meters that accept credit cards. But in Pennsylvania, it's local municipalities that are responsible for regulating parking, not the Commonwealth.
Before opening her Christmas gift from Jim, Pam shakes it and asks if it's pebbles from that beach in Jamaica. But they never went to Jamaica. They went to Puerto Rico on their honeymoon.