Preheat the oven to 350 degrees F (175 degrees C). Melt butter in a large skillet over medium heat.
Saute squash in butter until tender, about 10 minutes. Set aside.
In a large skillet, cook the ground beef, onion, and jalapeno, stirring until beef is evenly browned.
Drain off grease. In a large bowl, mix together the squash, eggs, and mayonnaise. Stir in the ground beef mixture and Cheddar cheese. Season with salt and pepper.
Pour into a 9x13 inch baking dish, and sprinkle cracker crumbs evenly over the top.
Bake for 20 minutes in the preheated oven, until heated through, and the top is nicely browned.