...could it be one of those remote worlds? If i could divert your attention to the worlds of Kingdom Hearts... Ansem always repeated that all worlds are connected, and with the GUMMI SHIP they are all in reach. But i've noticed that all the different worlds all belong to one realm that share the same time and the same space since the worlds were depicted much like planets in a solar system... but curiously... there are worlds that do not belong to the same time and space, which i personally call, "REMOTE WORLDS".
...If you need an example, I will state the 100 Acre Wood. It is a remote world not following the normal physics that the other worlds share, obviously it is not synchronized with the space aswell. and the only way to get to that particular worlds is by accessing the book, which is the only linking way to that world and out.
...so excuse me if i'm wrong but... Steam boat Willie is a world that goes against the usual flow of time, in a supposedly different space with supposedly different physics... so the light shown in both pictures could be the only pathway from the Disney Castle to the Timeless River, much like how the book is the pathway from Traverse Town to 100 Acre Wood.
...excuse me if it's a bit lengthy... i have a tendency for ramblings... hope it's something everyone can reflect on...