(This is probably old news to many of you, but I still wanted to compile it all here to hopefully inspire someone to make it an entry. I'm not using the emojis because they've fucked up my posts before and I don't know if it's fixed.)
Renowned YTPMV/video editor extraordinaire MowtenDoo seems to have a knack for starting bizarre fads based on very short, emoticon-like titles if the previous :D meme is any indicator. Now he's started a fad with just the blue jeans emoji and a sequence of aggressive edits of the GIF below to retro video game music.
He posted the original on November 1, 2016. It's reached 660,000 views.
It also used the GIF below of Blastoise playing the keyboard (edited from its sprite in Pokémon Diamond, Pearl, and Platinum), which became a recurring image in the fad alongside the pants guy.
On May 1, 2017, RedScreen posted a follow-up to MowtenDoo's video with an apple emoji added to the title. It's reached 710,000 views.
On May 20, 2017, MowtenDoo posted a sequel to his original with 2 pants emojis. It's reached 820,000 views (the most of any video here).
On October 27, 2017, MowtenDoo posted a version in tribute to Super Mario Odyssey with a hat emoji. It's reached 710,000 views.
On March 6, 2018, BagelBoy posted a mashup of his own walking duck meme and the pants guy with a duck emoji and pants emoji. It's reached 210,000 views.
On March 11, 2018, AutisticYui posted a bear emoji version. It's reached 410,000 views.
This video uses a GIF of a polar bear. This 9 month old thread on Tumblr with 9,000 notes has 4 versions of it at different speeds (below).
The polar bear GIF as a meme pre-exists the video (per the Tumblr thread), but it seems to have boosted its popularity. I found a version below on an archived 4chan /v/ thread and I think it's the original GIF's speed (and the smaller one its size), but I haven't found the original GIF itself.
AutisticYui has made several other polar bear videos over the past month, and dammit, I just love it to bits. It's why I made this post, but then I had to explain the whole pants thing as context (and it could use an entry anyway). If anyone knows what it's from, please let me know (and include it in the entry if you make it). I know this is a mess, but that's why I put it here and didn't shit out an entry.