See, the whole debate is one of generational differences regarding context and literalism.

Grandpa Joe was never faking it. It was never anything other than him being old and worn down beyond the ability to do more than stand up for bedding and clothing changes.

The news of Charlie getting the Golden ticket was transformational. Joy is transformational.

And that’s the key to understanding most of the movie.

Notice that all of the kids that get transformed, get transformed externally. Much in the way grandpa joe was.

But Charlie never changes on the outside because his inside, his true self, is filled with the joy of the world he enters via the Golden ticket.

Grandpa Joe is transformed by the power of Charlie’s joy. Remember, out sad grandpa joe that pushed Charlie into stealing fizzy lifting drinks. And, at the end, it was grandpa joe that would have given the gobstopper to slugworth.

But, again, Charlie saves grandpa joe from his own bitterness and anger (despite that anger being justified) by expressing his inner self in a true and honest manner. Charlie is hope, hope that joy and goodness can exist no matter how dark the world is. Grandpa Joe is a man that lost hope and joy as the world pummeled him with body wrecking labor, poverty, and hunger.

But, inside grandpa joe is a different form of transformative power. Love. He loves Charlie so much that Charlie’s joy can change him. Remember, one of the best definitions of love is another person’s happiness being intrinsic to your own.

Nobody who loves their grandson enough to overcome age and pain to then walk around a giant factory and still manage to rage against a man (wonka) who had dared crush his grandson’s hopes and joy can be truly bad.

That’s why grandpa Joe is our window into joy. We’re all cynical adults now, having journeyed on the same path as Joe, being worn down until all we can see is the surface of the event, rather than the true nature of the scene and the character.

But, when we were kids, it was different. We can remember Charlie being our door into that world of candy and song and happiness. It’s only after we begin transforming into grandpa joe ourselves that we forget that the entire movie is about joy and love making the entire world a better place.