This is not a new idea, at all. In general, lots of heroes have similarities to Christ. Because Christ is the biggest hero of all, since he conquered sin and death.
Also, articles have already been written specifically about WALL-E and Christ parallels. I just wanted to go over the ones I personally noticed.
... despised and rejected of men ...
Pretty much everyone who noticed WALL-E actually liked him very much. But at first sight, they often recoiled.
Behold, I was brought forth in iniquity ...
WALL-E came from humble beginnings. His place of origin was almost unknown to the people on the Axiom.
Husbands, love your wives, even as Christ also loved the church, and gave himself for it ...
If WALL-E is a picture of Christ, then EVE is a picture of the church. And WALL-E is devoted to EVE.
A new heart also will I give you, and a new spirit will I put within you ...
WALL-E converts people. Early in the move, people switch the color of their close from red to blue. WALL-E changes them. They also lose the screens in their faces. This is a metaphor to "waking up." WALL-E (directly or indirectly) ends up switching them all back to red, a picture of Christ changing hearts and setting captives free.
He put a new song in my mouth, a song of praise to our God ...
WALL-E is announced with a new song. Well, in the movie, it's an old song, but it's new to everyone on the Axiom. In fact, other robots sing the song to celebrate with WALL-E.
... to proclaim liberty to the captives, and the opening of the prison to them that are bound ...
After being sent to the repair ward, WALL-E sets the malfunctioning robots free, as well as EVE. They celebrate and singing in their new freedom, at least for a while.
... he was crushed for our iniquities ...
Yep, WALL-E was literally crushed. At the end of the movie, WALL-E is stuck inside the holo-detector as it's being deactivated. Otto forces the device closed, knowing it would gravely injure WALL-E. In doing so, WALL-E saves the day by allowing everyone to regain control of the Axiom.
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