Looking at the picture, we think we can just barely make it out ... it looks like ... Wander is waking up to discover that it was all just a dream! And then there's a knock on the door, and it's Argo the horse and all of the Colossi. And they've all brought birthday presents, and a Colossus-sized pizza with all your favorite giant toppings!
If you'd like to inspect the image for yourself for evidence of monolithic birthday parties, you can find it in slightly larger form after the break. We're not trying to make it a puzzle or anything -- that's just the size of the image that Ueda tweeted.