Set in the mythical city of Camelot, in a time before history began, this magical adaptation of the Arthurian legend follows young Merlin's enthralling encounters with the young Prince Arthur.
The kingdom of Camelot is a realm of legendary beasts and mysterious peoples. In this dangerous world, magic has been banned by the ruthless tyrant Uther Pendragon. Merlin, who was born with extraordinary magical powers, is taken as an apprentice to the court physician Gaius and as manservant to the headstrong Prince Arthur. However, with the practice of magic punishable by death, Merlin must take care when and where he uses his talents.
The Great Dragon, who lies imprisoned under the castle, informs Merlin that his gift has a purpose - to aid him in his destiny to protect Prince Arthur, who will one day lead a great and just kingdom. But Merlin has already discovered that following his destiny is not always an easy task.
Whatever the future holds, Merlin, along with Arthur, Morgana and Gwen, face many great dangers and exciting challenges as terrifying beasts and ruthless enemies stalk the kingdom of Camelot.Harry Melling is • Gilli • in Merlin

Although Harry Potter had been witness to Lord Voldemorts resurrection the Ministry of Magic refueses to make the return of the villain public. In order to be prepared against the attack of the dark lord and his followers Harry, Ron and Hermoine found Dumbledore's Army in which they teach their schoolmates defensive spells.
Harry Melling is Dudley Dursley
Notes: Actually Haley Joel Osment (The Sixth Sense) should have played Harry Potter. But because he thought an adequate adaptation to the screen of Joanne K. Rowling's books was impossible he cancelled his participation and the at that time 11 years old Daniel Radcliffe advanced.

During his third year at Hogwarts Harry Potter learns that the dangerous criminal Sirius Black has escaped from the prison in Askaban. The insidious Black tries to bring to an end what his master Lord Voldemort could not: Kill Harry! Or are things not as they seem?
Harry Melling is Dudley Dursley
Notes: After the death of actor Richard Harris Christopher Lee and Ian McKellen among others were in talks to take over the role of Albus Dumbledore. Eventually the part went to Irishman Michael Gambon.

In the second year at Hogwarts magician Harry has to solve the terrible secret of stone pupils, a mysterious diary and the infamous chamber of secrets.
Harry Melling is Dudley Dursley
Notes: When Harry comes out the door at the Knockturn Alley, a black clothed witch smiles at him - a cameo appearance of author Joanne K. Rowling. Richard Harris, the actor behind Professor Dumbledore, died after shooting had finished on October 25th, 2002 at the age of 72 on cancer. Harry Potter and the Chambers of Secret (2001) was his biggest success. The film made 968.7 million Dollars worldwide.
*The above listed work of Harry Melling makes no claim of being exhaustive. I took the information from DVD opening and end credits and not from sources on the internet.