Gwen, Freak's mother, is startled when she first sees Max. Max was showing Freak his room in the down under when he heard his mother calling for him. Freak decides it's about time that he heads out, so Max opens the bulkhead door for him. Gwen was looking around the backyard for freak, but she became frightened upon seeing Max. Philbrick writes, "She catches sight of [Max] coming out of the down under and it's like someone shot her. Like she's scared out of her mind" (20).
Max watches as Gwen pulls Freak away on the wagon and understands immediately why she is afraid of him. As a way to apologize, Gwen invites Max over for dinner, and even though Max originally doesn't want to go, he ends up really enjoying himself.
While at dinner, Gwen attempts to explain her actions by saying, "Sorry, Max. That is, I'm sorry we got off on the wrong foot. It's just, you know . . ." (25). She had a hard time putting it into words, so Freak interrupted and said, "What she means is, you're a spitting image of your old man" (25).
In other words, Gwen was startled by Max because he looks exactly like his father. Max responds to her by saying that everyone says that. At this point, Max decides that Gwen is OK - she's the first person to apologize to him and now she doesn't seem to be so uneasy around him.