How to use jQuery and OData to expand multi user field in SharePoint 2013?

I am using jQuery to query a Sharepoint 2013 list and expanding the AssignedTo field in order to get the user id. I was able to get the code working when the AssignedTo field only allowed one person, but when I changed it to allow multiple persons the code failed. This is the url I used for the single user but I don't have any idea of how I need to change this to get multiple assigned to users.

http://ift.tt/1GeqqAu('DEBUG - PLOT Compliance Exceptions')/items?$select=Id,AssignedTo/Title,Title,Comment,Exception_x0020_Type&$expand=AssignedTo/Title&$filter=(Status ne 'Closed' and Status ne 'Closed By System')&$top=5000

I would be OK with getting a string with all the user names if that is the only possibility. Once I get a valid url then I would need to step through the data. This is the code I am using to display the data in a jQuery datatable, so I'll have to know how the data is structured in order to be able to dig down and get all the user names.

        var call = $.ajax({
        async: false,
        url: _spPageContextInfo.webAbsoluteUrl 
            + "/_api/Web/Lists/GetByTitle('DEBUG - PLOT Compliance Exceptions')/items"
            + "?$select=Id,AssignedTo/Title,Title,Comment,Exception_x0020_Type"
            + "&$expand=AssignedTo/Title"
            + "&$filter=(Status ne 'Closed' and Status ne 'Closed By System')" 
            + "&$top=5000",
        type: "GET",
        dataType: "json",
        headers: {
            Accept: "application/json;odata=verbose"

        }

    });
    call.done(function(data, textStatus, jqXHR) {

        $('#issuesDataTable').dataTable({
            "bLengthChange": false,
            "bDestroy": true,
            "bProcessing": true,
            "aaData": data.d.results,
            "aoColumns": [
                {
                    "mData": "Id",
                    "fnRender": function(obj) {
                        var href = _spPageContextInfo.webAbsoluteUrl 
                            + '/Lists/DEBUG  PLOT Compliance Exception List/EditForm.aspx?IsDlg=1&ID=' 
                            + obj.aData.Id;
                        //return '<a href="' + href + '">' + obj.aData.Id + '</a>';
                        return '<a href="#" onclick="openInDialog(0,0,true,true,true,\'' + href + '\');">' + obj.aData.Id + '</a>';
                    }
                },
                {
                    "mData": "AssignedTo",
                    "fnRender": function(obj) {
                        if(obj.aData.AssignedTo.Title) {
                            var str = obj.aData.AssignedTo.Title.toString();
                            return str;
                        } else {
                            return "NA";
                        }
                    }
                },
                {"mData": "Title"},
                {"mData": "Comment"},
                {"mData": "Exception_x0020_Type"}

            ]

        });
    });
    call.fail(function(jqXHR, textStatus, errorThrown) {
        alert("Error retrieving Tasks: " + jqXHR.responseText);
    });

Thanks