There was a study a saw abstracted that suggests that cartoons are better than mothers at calming childrens' fears. I thought about it for a few minutes, and it made perfect sense:
Cartoons distract the child from the fear. Basically, it activates a completely different area of the brain. If the cartoon is salient enough, it can attract all of the child's attentive capacity, thus reducing the fear to zero.
Mothers soothe the child. They assure them that the fear is not real and that they are OK. Essentially, they are inhibiting the fear and associating the current state with the "things are OK" schema. This may solve the problem, but does not eliminate the fear activation completely.
So a good cartoon will always be better than a good mother for this kind of need. As long as the fear is not based on some real-world situation that must be addressed by the child, ignorance is bliss.