I saw this thing on twitter talking about how tommy would hide his visible zombie features from Charlie while staying with him and now all I can think of is Tommy, being the absolute gremlin he is, just rubbing dirt on his spots and Charlie thinking it's just normal Tommy behavior. Then Charlie trying to give him a bath and having to chase him around the base like you would a dog who doesnt want one until tommy ends up hiding in some small corner or underneath something. Then when Charlie ends up finding him, he's just so surprised by how the fuck Tommy managed to fit into such a small place that he just gives up.
