[spiel2001]

You need to create a method to handle the menu action. Something like this...

frame.popup = CreateFrame( "Frame", "$parent_Popup", frame, "UIDropDownMenuTemplate" );                

frame.menu = function()
    
    local popup = frame.popup;

    if popup then
                        
        local anchor = frame.popup;
        this.unit      = frame:GetAttribute( "unit" );
        this.name,
        this.server   = UnitName( this.unit );
                       
        ToggleDropDownMenu( 1, nil, popup, anchor, anchor:GetWidth()/2, anchor:GetHeight()/2 );
                    
    end            
 end