It's an in-joke.
Based on a video which has since been removed, clicking this extension's icon will cause a funny little gif of a Riolu to travel across your screen as some music plays.
CURRENT VERSION 3.5
Fixed an issue where the image didn't load properly.
Updated image, scripts, music, and fixed some bugs.
Riolu can only run across your screen if you're on a website, not the new tab screen or web store. Also make sure photobucket is unblocked.
Things will make more sense if you watch this video. https://www.youtube.com/watch?v=cMGerbYf2oY