Party Central (theatrical; 5:41)
Disney Movies; IMDb; Pixar; Pixar Wiki; Wikipedia
streaming sites: Disney+
This played in theaters before Muppets Most Wanted, but it's actually based on Monsters University. I watched it online, on Disney Movies Anywhere (though it has since been removed from the site). It's available on the Pixar Short Films Collection volume 3. It's a fairly amusing story of Mike and Sulley helping their fraternity brothers steal an awesome party from a more popular frat.
Sanjay's Super Team *
Riley's First Date? *
The Radiator Springs 500 ½ *
Party Central * The Blue Umbrella * The Legend of Mor'du * Partysaurus Rex