[Solved]-Highcharts: adding extra data to drilldown-Highcharts

Switch to using a point object instead of an array for the data.

    drilldown: {
        series: [{
            id: 'animals',
            data: [{name: 'Cats',
                    y: 4, 
                    otherValue: 100},

In the formatter your extra value will be under:

this.point.otherValue

Fiddle example.