I made pancakes. With 2 small children. And saved leftovers (thankfully, a 16 month old isn't exactly picky!). In a reusable container. Yes, slapping a piece of tin foil over a plate is more frugal than using a one-time ziplock (I can't bring myself to wash them, no matter what was in it.), but using a storage container was even more frugal (and our high-efficiency dishwasher takes out the "but, the water!" argument). Yes, it's one more thing to put away, but it's like a gift that keeps on giving!
You know those small cups of applesauce you stick in your kids lunches? Or the boxed juice? Or the pre-cut carrot sticks? Or frozen mashed potatoes? I had a bag of frozen mashed potatoes (about 1 bag would cover what I needed them for) in my grocery cart. They were "on sale" for 2/$5. When I headed to the produce section and saw a 10lb bag of russet potatoes for $.88 (you read that right!) I about keeled over in the middle of Safeway! ("Clean up in the produce section! Clean up in produce..."). I put the "easy road" back and put the "hard road" in my cart. I won't even get into the frozen vs fresh debate today. In my book, I was already ashamed at the frozen ones even being in my cart in the first place!
So, no, being frugal isn't always convenient, but you know what? I made my dish that the frozen potatoes would have just about covered, I still have at least 3 more meals of potatoes in my pantry, AND I have $1.62 left in my pocket.