As Meg enters STARKe Pharmaceuticals before the conference call with Mark McKinney, she walks past an extra who is leaving the building. When she gets off the elevator, she walks past the same extra on another floor.
As Joe has his lunch in the company cafeteria, he sips from a cup of Pepsi. The cup changes from large to small (large when Joe drinks, small when it's on the table beside him).
While driving down the freeway, the same background is seen twice. A Romano's Macaroni Grill is visible in two separate shots.
When Joe encounters Meg near her parking space, her cheeks appear alternately teary and dry.
Joe and Pat walk out of the building carrying umbrellas. Though everything is wet, you won't see any droplets in the puddles, nor on his tan pants or blue shirt.
Obvious stunt double of Joe crashing his shopping cart after racing with Mark in the Target store.
As Mark cuts Joe off in the parking lot, post production chose the wrong horn sound-effect. That sfx was intended for a car honking as is drove past.
When Natalie and her father Joe are in the car discussing his job, a clapper board can be seen next to them between the front seats. In the next shot a newspaper is there instead. The "Joe" part of the title is visible on the clapper board.
The scene where you see Joe passing the Macaroni Grill twice on his way from home to work is geographically incorrect. It appears on the left side of the highway which means he was actually driving towards Minneapolis, his supposed home, instead of away from it. In fact, the Macaroni Grill is even more west of downtown than where his office was located so he would never be on that part of the road going to or from work at all.
At 6:10, when Joe is driving into downtown Minneapolis to pick up his daughter, he [and all the other cars in the shot] are driving across a pedestrian bridge, the Stone Arch Bridge.
Chuck Scarett wears his Japanese headband (hachimaki) upside down throughout the film.