Prepare pudding mix and chill until ready to assemble. When cakes are cooled to room temperature, crumble into a large bowl. Toss with half the remaining white cookie crumbs and the chilled pudding. Put mixture into clean litter box. Put three unwrapped Tootsie rolls in a microwave safe dish and heat until soft and pliable.
Shape ends so they are no longer blunt, curving slightly.
Repeat with 3 more Tootsie rolls and bury in mixture. Sprinkle the other half of cookie crumbs over top. Scatter the green cookie crumbs lightly over the top, this is supposed to look like the chlorophyll in kitty litter. Heat remaining Tootsie Rolls, three at a time in the microwave until almost melted. Scrape them on top of the cake and sprinkle with cookie crumbs.