Maxi-mums

While driving in the car this evening, the following convo happened:

Max: Mom, my head won't open.
Me: WHAT?
Max: My head won't open...see? (Imagine him pushing his cheeks in on either side while sucking in his cheeks and raising his eyebrows)
Me: Why do you need your head to be open?
Max: Like the shirt.
Me: Like the shirt?
Max: Yah, the shirt.

That was the end of the conversation.
If anyone has any insight into this that would be of any help, please chime in. I'm clueless.