I feel that the transition from "Making monster" to "Pumpkin bouncing" was a little too sudden. At first, the focus of the film was entirely on the Monster-making Duo, and then it changed over to a mutant pumpkin with no warning or foreshadowing. It would have been smoother if, for the establishing clip, you had used a picture of the county-side looking at the Scientist's lab, but with the Pumpkin patch near the edge of the frame.

Then, things would appear to be centered on the Duo, but when the focus changes to the pumpkin, the viewers would remember the first scene, thus causing the twist to not seem quite so "Out of the blue."

Regardless of the above, it was still a very enjoyable brickfilm.
The animation was smooth, the pumpkin's bouncing was very well done, and that was a very good choice of music.