It is, indeed, a good thing that one of the gang back home isn't here to watch Hiccup struggle with the puppy. However, after another long moment of watching his friend deal with things, Toothless decides to help out. It would be bad if the determined little thing damaged something beyond repair, even though it doesn't seem possible.

Then again, Terrible Terrors don't seem so bad until they start swarming you.

Toothless shifts something on his harness with one of his back legs, and the fin that the puppy is clinging to extends all the way out. It's now far too big for a terrier to get its jaws around, and Toothless' tail pulls free.

Just don't say he never did anything for you, Hiccup.