I can buy the Wookiees on a spiritual quest with their snow globes. I have a hard time believing the others separately (some got there at different times) doing the same thing.

I can imagine a situation a la The Restaurant at the End of the Universe where Marvin isn't taking an elevator to the celebration. The Millennium Falcon parked with some other ships at the site that said "This way to join the Wookiee celebration".

But, as you say, it is a holiday special. And an horrific one at that. Mayhaps that's why we love it enough to generate over 700 posts.