This is the first time I've ever seen a movie make an effort like this to clear up so-called plot holes in the story. The plot holes here are really not plot holes at all, but strike me instead as just being some things that they wanted to tell a little more about, probably because they had such a good time making the movie. We don't need to know exact details of what happened when Shaun led the zombies away, and it's reasonable to assume that Dianne was killed by the zombies after she went after David, who was dismembered before our eyes. How Ed became a zombie-pet for Shaun is indeed curious, but it strikes me more as one last joke than an important plot point.
Nevertheless, these short animated comic-book style stories serve as a fun supplement to the rest of the movie, and I hope to see other movies take this example in the future. Simon Pegg narrates with the same comedic tone as the movie, mentioning how sometimes he had to sit and wait for the slow-moving zombies to catch up with him, so he could continue to lead them away from the Winchester. Nice work!
