Cut the spaghetti squash in half, scrape out the seeds, and place it in a rimmed baking dish face-down with 1/4 cup of water. Bake at 375 F for 1 hour, or until soft. Once cooked, set aside until cool enough to handle. Once cooled, scrape the squash out into a large bowl.
For the ranch dressing, whisk the mayo with the lemon juice and dill until smooth.
Scoop 3/4 of the cooked spaghetti squash out of each shell and into a large bowl, leaving some remaining around the edges.
Add, chicken, hot sauce, ranch dressing, and celery to the bowl, stirring well to combine. Pour the mixture back into the spaghetti squash shells and bake for 30 minutes. Remove from oven, let cool for 5 minutes, then garnish with green onion and serve!