Children playing on the swingsets at Waldo Street Tot Lot were treated to a raw, uncensored display of hot pug-on-pug action, sources reported Tuesday. 'First the one doggy got behind the other doggy,' said Andy Haupert, 6. 'Then the first doggy tried to get on top of the other doggy while the other doggy tried to run away. It was really funny.' The canine copulation has been the most talked-about animal-related playground incident since June, when a pigeon crapped all the way down the slide. 