Starting with macOS Sierra (10.12), any application distributed outside the Mac App Store runs from a randomized path. This breaks many features in Mosketch. In particular, it is not possible to use the shortcuts to load the embedded characters like Mosko and Okto.
(in the following, we suppose you installed Mosketch in the /Applications folder. If not, please adjust the following command lines accordingly).
To solve this issue, first ensure that Mosketch does have the com.apple.quarantine extended attribute. In a Terminal, do the following:
sudo xattr /Applications/Mosketch/Mosketch.app
You should get:
Now remove this attribute:
sudo xattr -r -d com.apple.quarantine /Applications/Mosketch/Mosketch.app
You are now ready to go and to enjoy animating with Mosketch!