• Connect adjacent dots with vertical or horizontal lines to make a single loop.
• The numbers indicate how many lines surround it, while empty cells may be surrounded by any number of lines.
• The loop never crosses itself and never branches off.

• Link to Penpa version (let me know if there's a mistake, I transcribed this manually)
– HTM
Commented Apr 1, 2021 at 4:52
• Haha! I had a feeling the seasonal tag was going to prove appropriate here! :)
– Stiv
Commented Apr 1, 2021 at 6:03
• @Stiv yeap, adding the tag :) Commented Apr 1, 2021 at 8:34
• An alternative (and perhaps superior?) version of the joke involves a rot13(yratgu fvk ybbc fheebhaqvat gjb guerr pyhrf) :) Commented Apr 1, 2021 at 9:07
• @happystar yes!! I once found it published by someone and I was dumbfounded :)) Commented Apr 1, 2021 at 9:19

Yep, that's it. All those clues for just a measly square. (I guess that's why this puzzle's tagged !)

Explanation:

We start by

marking the edges where the loop cannot pass through due to the 0 clues:

Next,

we progressively mark off edges coming off of dots where the other three edges (two for a border dot, one for a corner dot) coming off of them are marked as unusable. We continue to do this until we reach a state like this - note the square at R10C16:

And here's the coup de grâce:

It appears that we're able to make a connected loop spanning the entirety of the grid, but actually we can't (!) due to the edge marked with the star below not being usable: Thus, we are forced to use the square mentioned earlier for our loop, giving us our final solution.

• Nicely done and well explained! XD Commented Apr 1, 2021 at 8:35
• @athin Thanks, this is a really nice construction!
– HTM
Commented Apr 1, 2021 at 8:37