YouTube API example wrapping existing iframe elements.

youtube-embed-existing-iframe.js

/* Youtube */
window.onYouTubeIframeAPIReady = function () {
	window.youtube_players = [];
	$('.video_container.youtube').each( function () {
		// Only set the play functionality up if the video has a thumbnail
		if ( $(this).find('.video_thumbnail').length ) {
			var thumbnail = $(this).find('.video_thumbnail'),
				play = $(this).find('.video_play'),
				player = new YT.Player( $(this).children('iframe').attr('id') );
			window.youtube_players.push( player );
			var thumbnail_height = thumbnail.find('img').height();
			$(this).height(thumbnail_height);

			// Play button
			play.click( function () {
				player.playVideo();
				thumbnail.fadeTo( 200, 0, function () {
					thumbnail.css( 'z-index', 0 );
				});
			});
		}
	});
};