Every applet can run in multiple threads.
But no application ever calls them from the AWT drawing and event handling thread. Many browsers allocate a thread for each applet on a page, using that thread for all calls to the applet's major milestone methods. Some browsers allocate a thread group for each applet, so that it's easy to kill all the threads that belong to a particular applet. In any case, you're guaranteed that every thread that any of an applet's major milestone methods creates belongs to the same thread group. Below are two PrintThread applets.