Add melted butter to crushed Oreos and toss to combine. Press into an ungreased 9x13 cake pan to form a crust, and place in freezer for 30 minutes to firm up.
While crust is chilling, soften the orange sherbet on the counter until it’s easy to spread but not melted. Spread softened sherbet over Oreo crust. Return to the freezer and chill while you're whipping the cream.
In a large mixing bowl, combine heavy cream, powdered sugar, and vanilla; whip until stiff peaks form. Decorate the top of the dessert with the remaining Oreo cookies, chopped, and sprinkle with Halloween sprinkles.
Cover pan with plastic wrap. Freeze 2 to 3 hours until the sherbet is firm. To serve, thaw slightly and cut into squares.