
That's Jeanette Eymann, Jack's long-time secretary who always worked on the scripts, the odds are probably good that's even Jeanette's handwriting on that Drear Pooson script excerpt above.
She did a bunch of bit parts, once you start seeing her, she pops up everywhere. She's even supposedly in the "Pasadena Fan Club" episode above, though I couldn't ID her definitively in my copy.
Also pictured are Margaret Brayton, Stevie Wooton and cult-movie kid actor Charles Herbert (from THE FLY, 13 GHOSTS, TWILIGHT ZONE, etc).