Question: Why can't Glenn understand anything Cole signs, leaving Iris to translate? Glenn knows and uses sign language when talking to Cole so it seems strange that he doesn't know anything that Cole tells him when Cole uses sign language.
Answer: Glenn was passionate about music and wanted to be a great composer, something relatively few people are able to attain. At least initially, taking a part-time music teacher position was not what he wanted to do or be - but it provided the resources to support himself/his family while giving him enough time to pursue his dream (music composition/opus). Glenn had an on-again/off-again (mostly "off") relationship with his son Cole, perhaps sometimes due to his lack of commitment, time constraints, frustration, sense of failure, and emotional pain over his belief that he could not successfully nurture the love of music in his near-deaf son. (Glenn was aware of the difficulties Beethoven had.) In some ways, Glenn (selfishly) was saying, "I don't have time for this" (communicating in sign language or providing the fatherly devotion and sacrifice necessary to understand and develop a good rapport with his "special needs" son).
Question: In this version of the story, why does the Mouse King have seven heads?
Answer: The original 1816 story "The Nutcracker and the Mouse King" by ETA Hoffmann features the seven-headed Mouse King. Since then there have been numerous adaptations and re-imaginings of that story in literature, on stage and screen in different forms. In the classic versions the Mouse King has seven heads wearing seven crowns, other versions he has only one head, and in a few versions three heads. In the original and other adaptations the number seven is specified several times: Marie Stahlbaum is seven yrs old; the seven-headed Mouse King; the seven steps backwards; seven little crowns. The makers of this animated movie chose to feature the classic Mouse King.
Answer: Iris knows and understands sign language much better than her husband. Glen can communicate on a basic level, but when Cole is ready to tell off his father, he wants to make sure Glen understands exactly what he's saying. Remember how Glen didn't know the sign for 'a***hole'.
Brian Katcher