Potters Alive... with a twist

The potters, james and lily, rose from the dead 12 years after the fatal attack on their home. they go to dumbledore to find that...

Their son hasn't been seen since that attack, but he is alive, because dumbledore frequently checks on him, using diagnostic spells.

When the name Harry Potter comes out of the goblet of fire, and the next morning, a young man is found outside of the castle, what will happen?

The twist is this- Harry Potter goes by the name of Hiccup Horrendous haddock the third, and rides a night fury -wait for it- named Toothless.