  The number of characters in a movie is an interesting feature. However, it is
non-trivial to measure directly. Naive metrics such as the number of credited
characters vary wildly. Here, we show that a metric based on the notion of
"ecological diversity" as expressed through a Shannon-entropy based metric can
characterise the number of characters in a movie, and is useful in taxonomic
classification. We also show how the metric can be generalised using
Jensen-Shannon divergence to provide a measure of the similarity of characters
appearing in different movies, for instance of use in recommender systems,
e.g., Netflix. We apply our measures to the Marvel Cinematic Universe (MCU),
and show what they teach us about this highly successful franchise of movies.
In particular, these measures provide a useful predictor of "success" for films
in the MCU, as well as a natural means to understand the relationships between
the stories in the overall film arc.
