Use foil to line an 8x8 pan, with overhang on 2 of the sides so it can be used like a sling. Spray the foil with cooking spray.
In a food processor or high power blender, pulse animal crackers, brown sugar, and salt until evenly fine crumbs (about 1 1/4 cups crumbs). Add melted butter and pulse until crumbs are evenly moistened, about 10 pulses. Press crumbs evenly and firmly into the bottom of the prepared pan.
Bake until golden brown, 15-18 minutes.
Meanwhile, in a medium bowl, stir cream cheese, zest, and salt with a rubber spatula until combined. Add sweetened condensed milk and whisk until incorporated and no lumps. Gently whisk in the egg yolk and lime juice until incorporated. Pour filling onto crust; spread to corners and smooth surface with the rubber spatula.
Bake until set and edges begin to pull away slightly from the pan, about 15-20 minutes. Cool on rack to room temperature, 1 to 1 1/2 hours.
Cover with foil and refrigerate until chilled, at least 2 hours.
Lift bars from pan using the foil sling and cut into 16 squares. Sprinkle with toasted coconut, if desired. Enjoy!
Refrigerate leftovers for up to 2 days; crust will soften slightly.
Notes
Want more? Double recipe and make it in a 9x13 pan. Increase baking time by a few minutes, as needed.3-4 hour cooling time is not included in the time estimates above!