Contrary to the way too popular pins going around, Nagini is not the same snake that Harry released from the zoo in Philosopher's/Sorcerer's Stone. The babies playing Harry aren't the same as the kid playing Albus either.
1. Voldemort on the back of Quirell's head (Sorcerer's Stone) 2. Teenage Tom Riddle (Chamber of Secrets) 3. Baby Voldemort (Goblet of Fire) 4. Regular Voldemort (Goblet of Fire, Order of the Phoenix, Deathly Hallows Part 2) 5. Kid Tom Riddle 6: "Tween" Tom Riddle