Casey tells Teddy he "wasn't the best babysitter" but the actor who plays Casey is a year younger than Jesse Plemons.
When Teddy mispronounces "shibboleth," Michelle mocks him for using poor grammar. But grammar is the set of rules for how a language is structured (e.g. order of words in a sentence, inflection of words etc.), a mispronunciation is not a grammatical error.