Cook & drain pasta according to pkg directions; set aside (keep warm).
Meanwhile, cook meats and onion; stir in spaghetti sauce, mushrooms, and herbs.
In the crock-pot, spread ONE-THIRD of the meat over the bottom, then ONE-THIRD of the noodles, sprinkle ONE-THIRD of the pepperoni slivers and one cup of each of the cheeses.
Repeat twice with remaining meat-sauce, noodles, pepperoni and cheeses.
Actually, you can do this in whatever order you like -- but, please, finish with cheese on the top!
Cover crock-pot and cook on LOW for 3-4 hours (the smell will be too much to believe!
).
Cheese should be nicely melted and browned to a crunchy, delectable goodness around the edges.