Place a baking sheet in the freezer to chill, about 20 minutes. Line the baking sheet with parchment paper and coat with cooking spray. Spray the insides of eight 3-to-4-inch cookie cutters and place on the parchment. Fill each cutter halfway with small scoops of ice cream and sherbet (about 1/2 cup of each), alternating to create a marbled effect. Repeat with another layer to fill the cutters. Smooth the surface of each with an offset spatula or the back of a spoon. Cover with plastic wrap and freeze 1 hour. Meanwhile, place another baking sheet in the freezer to chill, then line with parchment and coat with cooking spray.
Remove the cookie cutters from the freezer a few at a time, and use the plastic wrap to push the ice cream mixture out of the cutters. Insert a wooden stick halfway into the pop; smooth the surface if needed. Lay the pops on the other lined baking sheet, cover with plastic wrap and freeze until firm, about 30 more minutes.