Goofs

Walter asks his former neighbor if she "still" has keys for Skyler's house. She does, however, Skyler had changed the locks earlier in the season.

When Gus arrives as the nursing home, it shows him parking in front of the building (next to the handicapped spaces), but a few minutes later, he gets out of the car and walks across the parking lot (and through the landscaped circle) to get the front door. Additionally, the landscaped circle is differently landscaped from the overhead shot to the this shot.

The agent flips the top page of his notebook twice during the meeting with Tio Salamanca and Schrader.

The same hospital staff member who walks off the elevator with Walt walks back onto the elevator moments later.

When Jessie is questioned by the FBI about ricin, they state they will just wait for the results of the toxicology screening and later release him saying the toxicology screen revealed no ricin. There is no medically or legally accepted test for ricin poisoning.

During the explosion at the nursing home that claims the lives of Gus, Tio and Tyrus, only the explosion is seen, no fire at all. However during the TV broadcast seen at Walter house says the fireball completely consumed the room. The fireball would likely have been seen when the door was knocked off the hinges.

The striker button on Hector (Tio) Salamanca's bell is bent in all other episodes except for this one. In this one the striker is straight, but this may due to Walter modifying the whole setup in order to set the explosives with the striker as a trigger. To avoid a failure, he might have wanted to assure the proper functioning of the striker.

When Walt and Jesse exit the lab after rigging it to blow, there is a plume of smoke billowing from the lab's entrance in the laundry. The timer Walt set to spark the blaze didn't engage until after Jesse pulled the fire alarm.

What was seen isn't smoke. It's steam from the machine that the laundromat employee is working at, as Walt and Jesse walk by.

The cotton plug inserted into Bryan Cranston's right nostril used to make his nose appear swollen under the bandage (following the car wreck with Hank) is visible in a shot when he is on the roof of the parking deck of the hospital in the last scene when he is talking on the phone to Anna Gunn.