After Max walks out on the Suck E. Cheese's, Goofy says he just wants them to spend time together as father and son. Max more or less says he wants nothing to do with his dad, ever again. You can just feel poor Goofy's heart breaking.
Max: This is the stupidest vacation! You drive me from home, and jam me in this dumb car to drive me a million miles away TO SEE SOME STUPID RAT SHOW! (inhales) Call me when the trip's over.
Goofy's line to Max near the end hits a little too close to home.
Max: I'm not your little boy anymore, Dad! I've grown up! I've got my own life now! Goofy: I know that! I just wanted to be part of it! (beat) You're my son, Max. No matter how big you get... you'll always be my son.
Max pounds the roof of the car on the word "not," eloquently conveying his frustration, and adding to the quality of the scene.
The hug between Max and Goofy after Max saved his father from falling in the waterfall.
Goofy's completely destroyed expression when he discovers that Max changed the road map.
And, for that matter, the entire scene surrounding it too. When the map-change is first revealed by Pete, Goofy actually calls Pete on his accusation, marking the first (and only) time in the movie that Goofy actually stands up to Pete's belligerence. Yet despite Goofy insisting he didn't need to follow Pete's advice and check the map to see if it had been altered (because "I trust my son", showing just how much Max and Goofy's relationship had improved), the next scene shows Goofy getting into his car, clearly wrestling with himself on what he should be doing. He grows angry with himself for not following through on his own words and is about to go back inside, when he pounds his fist on the steering wheel causing the glovebox to pop open, discovering the truth... that Pete was actually telling the truth this time. Then, just because poor Goofy hadn't been kicked enough at that point, he gives Max one last chance to come clean in a Secret Test of Character when he demands to know which turn they need to take to get to Lake Destiny; despite a crisis of conscience, Max sticks to his original plan, destroying Goofy's faith in his son.
Goofy's bitter response to Max's attempt to explain. Hearing Goofy being genuinely hurt and angry is just devastating.
Max: Dad, listen, about my directions... (Goofy turns his back to Max) Will you listen to me? I've gotta tell you something, Dad! Goofy: Why bother? I'm probably too stupid to understand anyway, right?
The scene where Max and Goofy are trapped in the car overnight. When Max expresses amazement over a trick Goofy uses to open a can of soup, Goofy explains that his father taught him that, prompting this regret-filled exchange: