Other mistake: When Homer kicks over the bomb, the time on the bomb decreases by half. Because of this, Krusty yells "Get outta here!" to Homer. However, Homer was standing in front of the bomb and Krusty was standing behind Homer, which means Krusty's view of the bomb was completely blocked, so he couldn't possibly have seen the bomb lose half of its time. He was definitely reacting to bomb losing half of its time, as he is shown looking straight at it just before he starts yelling at Homer.
Add timeCasual Person
Other mistake: When Homer falls through the roof into the house we see Grandpa sitting somewhere other than the ground floor or the second floor. The problem is the Simpsons' house has an attic on top of the second floor and below the roof. The length of the attic's floor and the house around it are totally the same, so really what we should have seen was the attic, not Grandpa sitting somewhere.