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.
Hiccup’s first encounter with Toothless is fleeting. Hiccup aims his catapult and is looking for something to shoot at specifically, the Night Fury. when Toothless flies across and is briefly silhouetted against the starry night sky. Hiccup roughly gauges where the dragon would be in his flight trajectory before shooting, and successfully strikes the dragon mid-flight, as evidenced by the roar and howl he emitted while visibly plummeting toward the ground. Though Hiccup was ecstatic at having finally shot down a dragon, and a Night Fury no less. And at last Toothless became Hiccup’s best bud in life.