Sometimes penguins don't always behave themselves when they are being weighed

Once a month zookeepers give these rockhopper penguins at Milwaukee Zoo in America a friendly weigh-in.

The keeper hands the penguins a small fish to get them walk onto the scale, to weigh them and make sure they're healthy.

At times, they jump over the scale, or plop two at a time on the scale in the pursuit of a fishy treat.

Watch the video to check out these penguins naughty ways!