There is so much I liked about this animation!
**Spoilers ahead**
From Willard straight up stealing a pizza shop to make a pizza to his methodical movements, nearly every moment in the animation has something interesting going on, even him just adding ingredients (I especially liked how he fell out of the can at the beginning and him falling backward while putting in salt and something else. Second only to him shooting the creature so many times). The silliness was outstanding, yet it stayed focused on the mission of making the pizza and you weren't afraid to get pretty dark with it.
The quick progression segments of the animation are a major plus in my book. Most of it strikes a good balance between staying just long enough to where you can tell what's going on and not lingering long enough to get boring. You could say it has a natural flow at times (those were probably my favorite parts, especially the attempts at cooking part). It was also good of you to break this flow (like the basement part) as this keeps it from getting stale (though I have to say it stayed a little too long on the basement, specifically the cockroach part).
Also, thanks for getting straight to the point at the beginning. Some might have had a character stumble across a pizza recipe in a cook book while looking through it, have a moment that zooms in on the picture of the pizza with angelic background noises, and then cuts to the character trying to make it. Willard knew exactly what he was going to do from the beginning, no lead up needed.
Out of all of it, Willard shined the brightest (as he should being the star). His expressionless and near sociopathic behavior were awesome (I can't imagine I'd ever say that about a person in real life, but that's beside the point).
For suggestions, while all the things that happened after falling back to Earth were interesting, I think some of them could have been funnier. For example, maybe after the pinball affect with the buildings, have the building on the right blink "New High Score" in the windows or something. Or for the plane part, have Willard almost hit a bird, miss, and then the bird gets sucked into the engine of the plane. Just some ideas; not sure how good they are. I did like the bad stand up comedy part and the resolution of the black creature.
Overall, excellent work! You've got skills, sir!