On a limited budget it's somewhat hard to animate someone running without making it look jerky. As recently as The Perils Of Penelope Pitstop, animators tended to draw legs moving with very little bending of the knee, sometimes at even a full run. In real life, this would be more than a little painful, as shown in this animated insert from Sesame Street.
The preferred trick around this is to [...] [tvtropes.org]