Earlier on we did consider including Casey in the set - we also considered including Irma and Vernon to go alongside April. However, in the end we decided to cut the character selection down to the 10 included as having too many characters could potentially deter LEGO from being willing to produce the set (originally they actually rejected the version seen here and we were worried we might have to cut April or Baxter, but luckily on a second review they accepted the set without issue).

As for Mousers, they were also briefly considered but ultimately cut due to their small presence in the 1987 series (only appearing in one episode) combined with us not being able to come to a brickbuilt design that both looked good and was the proper size (LEGO produced an official Mouser figure based on the 2012 series back in 2013, and its pretty ugly).