Quirby's seemingly clever assortment of Pixels

[Kelvin]

You should give the running cycle an even number of frames. An odd number makes it look like he's limping. A good way to do it is to have one leg do a full animation cycle, then copy it and darken it, offset the frames by half the number, and then layer the background leg behind the foreground leg. It'll make them look even and consistent. Take a look at my running cycle here: