Classic Tweening Problem when Animating walk cycle

Hi,

Ignoring the character on left, my character rig keeps doing this weird twirling thing with their foot. I'm very new to animate and don't understand why this keeps happening with all my characters rigs (this problem has happened before). Sometimes the arms will go twirl all crazy. I've also seen size of certain body parts get super big and small. This is all happening in the inebetween tweens. I'm trying to animate through classic tweens. This character rig is all made up of symbols and I did the proper parenting, so it's difficult for me to troubleshoot this problem.