I try to plan out our dinners for the week -- although I often forget and don't get items out of the freezer to thaw or run out of time, etc. So spaghetti is a favorite meal to substitute, but it does get old.
This recipe from Taste of Home is a great twist on Italian spaghetti. Just be sure your fajita mix is MSPI-friendly. (I actually used taco seasoning, which worked well.) I didn't have green chilies on hand, so I left them out. And I definitely don't think the dish suffered for it. Very good!