3d High Charts Multiple Series inside of Drilldown

I am having a very big problem in high charts to have multiple series using drill down and also while clicking back button

This is the js function which i am using where i can create a multiple series while drill down but while returning back the previous data are merging with the current data

function hello() {

            var odata = [{
                name: 'Jan',
                y: 50,
                drilldown: 'animals'
            },
            {
                name: 'Feb',
                y: 52,
                drilldown: 'animals'
            }

            ];

            $('#container').highcharts({
                chart: {
                    type: 'column',
                    margin: 75,
                    options3d: {
                        enabled: true,
                        alpha: 15,
                        beta: 15,
                        depth: 50,
                        viewDistance: 25
                    }
                },
                title: {
                    text: 'Employee Leave status, 2013.'
                },
                subtitle: {
                    text: 'Click the columns to view more.'
                },
                xAxis: {
                    type: 'category'
                },
                yAxis: {
                    title: {
                        text: 'Total Number'
                    }
                },
                legend: {
                    enabled: false
                },
                plotOptions: {
                    series: {
                        borderWidth: 0,
                        dataLabels: {
                            enabled: true,
                            format: '{point.y}'
                        }
                    }
                },

                tooltip: {
                    headerFormat: '<span style="font-size:11px">{series.name}</span><br>',
                    pointFormat: '<span style="color:{point.color}">{point.name}</span>: <b>{point.y}</b> Number of days<br/>'
                },
                series: [{
                    name: 'UN Over-All for year',

                    colorByPoint: true,
                    data: odata
                },
                {
                name: 'Pl Over-All for year',
                colorByPoint: true,
                data: odata 
                }],


                drilldown: {
                    series: [{
                        id: 'animals',
                        name: 'Animals',
                        data: [{
                            name: 'Cats',
                            y: 4,
                            drilldown: 'cats'
                        }, ['Dogs', 2],
                ['Cows', 1],
                ['Sheep', 2],
                ['Pigs', 1]
            ]
                    },{

                        id: 'cats',
                        data: [1, 2, 3]
                    }]
                }




            })

        }

I need to have multiple series at each drill down and also i am having multiple drill downs

Here is the fiddle

http://jsfiddle.net/mohamedmusthafac/x5E2Y/1/

Just click jan->then any one bar->then click back->then click another bar of same pair->Bug(Series colliding)