Drain garbanzo beans. Pour them into a mixing bowl and smash them with a fork. Set aside.
Add the onion, garlic, egg, juice of the lemon, and all of the spices to a food processor or blender, and puree until smooth. Pour over smashed garbanzo beans.
Mix together with a fork, adding the breadcrumbs in little by little until the mixture is wet and sticky but can still nicely be formed into balls.
Pour olive oil into the bottom of a large crockpot.
Form golf-ball sized patties of falafel and slightly flatten. Dip each side into the olive oil and then nestle into your crockpot. It's okay if they overlap or are on top of each other.
Cook on high for 2-5 hours.
In a medium bowl, mix together the yogurt, celery salt, dill, and juice of the lemon. Season with salt and pepper, and refrigerate until ready to serve.
When ready to eat, add some shredded spinach to each tortilla; add falafel and top with yogurt sauce. Serve with grapes on the side.