The scene where Angela talks to Pam about her suspicion that Dwight killed her cat took a long time to shoot because Jenna Fischer and Angela Kinsey, who are good friends in real life, couldn't keep a straight face when talking to each other. It was so bad that they stopped shooting the scene and the director told them both to take a break while the director filmed something else and they came back to it later in the day.
Angela Kinsey (Angela) was pregnant during the filming of most of season 4, that's why the cameras never show her stomach.
Filming the run was not easy for the cast. On John Krasinski's YouTube series Some Good News, he and Steve Carell commented on how the temperature that day was a sweltering 105 degrees.
When Michael is seated on the grass near the end, you can see the 'No Parking' signs the real production crew attached to telephone poles and street lights to keep the parking spaces behind Michael free from cars.
In the end when Meredith is visiting Michael in the hospital, the sucker that Michael has was given to him by his pediatrician from a deleted scene.
When Angela holds up photos of Sprinkles the first photo is of them on a picnic blanket. In the second photo they're at Angela's desk and the computer wallpaper is the first picnic photo.
From this episode on, the closing credits will also play the intro music instead of no music.
The full name of the titular Fun Run is "Michael Scott's Dunder Mifflin Scranton Meredith Palmer Memorial Celebrity Rabies Awareness Fun Run Pro Am Race for the Cure."
In this episode, Creed reveals his age as being 81 years old. Implying that he was born November 1st, 1926.
Kevin's "PB & J" (Pam Beesly and Jim) line is a play on the fandom's real shipper name for Pam and Jim, "Jam."
Pam mentions going to the flea market at the drive-in. The drive-in/flea market she refers to is the Circle Drive-In on US Route 6 in Dickson City, PA. In late spring/summer it is in fact a real flea market that takes places on Sundays from 7am-4pm. It's also an actual operating drive-in movie theater in April to September that shows double features on Fri/Sat/Sun nights.
Jim mentions mountain biking on Montage Mountain (now called Snö Mountain). Mountain biking is not permitted on the mountain.