Hiccup and Toothless have a very close bond that has gotten stronger as the franchise continues. Both Hiccup and Toothless lead Berk as leaders of their respective species. They first met in the first film of the franchise, and have been featured in every show and film since. Toothless is also a lot more playful than he was when he first met Hiccup. It is also revealed by Valka that Toothless is the same age as Hiccup. This may be another reason for how well the duo gets along. This scene is the first touch of toothless and Hiccup. They turned in to best friend because hiccup let Toothless come to him slowly with trust. And of course Toothless did not open up to Hiccup immediately. He was suspicious, growled a lot, and opened up only very slowly. But the fact he ever took to trusting Hiccup at all is incredible in and of itself. Not only that, but he started opening up even before Hiccup started fixing his tail.