Bonnie Somerville (Rachel Hoffman) played Ross's girlfriend, Mona, in season 8 of Friends. Tate Donovan (Jimmy Cooper) played Rachel's boyfriend, Joshua, in season 4. Ross & Rachel, of course, end up together in season 10.
When Ryan goes to the hospital after Marissa calls and ask him to, he runs out the door of the pool house. He walks through the frame, revealing that the door is missing its glass panel. The door handle is visible on the right as he walks away from Seth. This is incorrect. If you look closer you will see that Ryan goes out the left door which swings outward toward the main house. The door handle mentioned is the handle for the right door.
Sandy notes Rachel Hoffman is 33. That would make Rachel three years older than Bonnie Somerville, the actress portraying the character, ironic since Ben McKenzie (Ryan), Adam Brody (Seth) and Rachel Bilson (Summer) are all considerably older than their characters.