Animations are all from 1080p source, pissing animations are done by masking to reduce the size, too bad about the rest. Screenshots have been run through waifu2x denoise level 1 with some color enhancements.
And because i absolutely HATE hentai, i decided to make 1080p gifs that cannot fit into tumblr - i don't think ants appreciate hentai, if they do, fill free to give me a heads up and tell which nest you're from.
Anyway, about the 16:9 aspect, i apologize to the time travelers from the 1990s that i simply could not bear to squash apples into bananas to fit your CRT monitors. And to all the people who insist 720x480 is correct because that's what it came in, hey there are less fat people than you think, consult your nearest optician for a better pair of glasses. (PS. Mine came in 1920x1080)
Well, your source for that particular video is from DL version and it came in 1920x1080. So this is unrelated, but all DVDs are still bound to 720x480. Because legacy DVD players are not compatible with other formats.
Ratio of 720:480 is [13.5:9], but the aspect ratio of DVD video is still [16:9] (or [4:3]). The reason is that analog TVs used non-square rectangular pixels. The format is never meant to be pixel-by-pixel resolution and you always need to stretch the video according to instructions. Most of devices/softwares are doing this automatically so you didn't notice you were watching stretched TV/DVD all the time, but they've been broadcasting/recording squished images just to counteract non-square pixels, until they switched to the digital signals. Then people started pirating, some of them didn't understand the difference between pixel dimensions and correct ratio for watching. They ripped the raw video data and removed the DVD IFO that clearly states "this video must be played in 16:9 aspect ratio". Another shout out to VLC media player where its snapshot function ignores video's metadata by default, creates "raw resolution" screenshots out of properly encoded DVD video file. Those stretched/squished images are just ugly, they would have known there is something wrong with the procedure. But no, 720x480 images spread across the internet by clueless people. 720x480 is not a valid resolution in any way since we all use square pixels. When in doubt, just convert them to 16:9.