i too had the same thought by using jQuery,
but unfortunately the answer is you can't.
Reason to think that you can't:
Usually when creating a server control during design time or dynamically, you might observe an attribute
runat="server"
in the tag, indicating that it's a server control.
just for fun: try adding an attribute to a control as
$("#labelid").attr("runat","server");
dynamically in a button click.