What is the fine-grained topic of the following text: I doubt that when the team that created the TV version of Horrible Histories were putting the show together they thought that what they were making would not only became one of the most popular children’s series in the UK, but would also have massive crossover appeal, with adults tuning in for the educational silliness. Only return the topic.
The popularity and crossover appeal of the TV version of Horrible Histories.