Fat penguins: they're a thing. They're not just chubby because they're stress-eating squid, however; male King Penguins gain weight so that they can live off their fat reserves while protecting their eggs. But this can make the penguins less agile,so researchers at the University of London, led by Astrid Willener, took on the very important task of putting penguins on treadmills to see how their agility changed with weight loss. 

The Guardian provided this hilarious, if not quite journalistically sound, video from the experiment where the original video has been sped up and paired with jaunty music, giving the experiment a Benny Hill vibe: