Maybe it's not off-the-cuff creative babysitting ideas if it's rehearsed, but the key is that you need some way to entertain the kids and the other ideas aren't options. Maybe you're waiting outside the dance studio to pick up a sibling, or you're at the soccer field with one child while his sister plays a game. Or it's bedtime and not possible to try the other ideas. Here are some that may work. Work on the kids' imaginations with these fun, spur-of-the-moment creative babysitting ideas.
1. It's bedtime and the children don't want to go to bed. It hasn't gotten argumentative yet, so you propose a game to play on their way upstairs (or at the beginning of the hallway to their bedrooms). The kids start at the bottom of the stairs. You show them any small item that can fit in your fist--a quarter, your "magic stone," etc. Put your hands behind your back and put the item in one hand or the other. Bring both hands back in front, and one child guesses which hand the item is in. If he is correct, he moves up a stair (or two, depending on how late it's getting). If he's wrong, he stays. Now it's the sibling's turn. This works even if there's only one child, as he must still be "right" to head up the stairs. This, in their minds, delays bedtime and makes it more fun to go to bed.
2. Dress-up or costume games. This works for boys, too. The idea is to challenge the children to look as much like a... pirate, or a bear, or any other person or animal you or they choose. Give them a certain amount of time to see what they come up with. Encourage them to be creative and use non-Halloween costumes!
3. Getting from here to there and back. Believe it or not, this creative babysitting idea entertained a bright 8-year-old girl for a good half hour. Establish a start and end point, maybe 30 feet from one another. Time the children, one at a time, on how long it takes them to get from the start to the end, and back to the start, using any various way to get from here to there and back. Hope on one foot, crab walk, "swim," baby steps, tiptoe, etc. They'll love the challenge of moving for that long in a "fun" way, as well as the time challenge.
4. That brings up Simon Says and Mother May I. Similar games, neither of which require props. It's possible kids may not have heard of these games, but they're easy to teach and fun.
5. Charades is a great game to play, but you need to have a good amount of ideas top-of-mind. Animals tend to be the easiest, then think "careers"--a fireman, a doctor, a teacher, etc.
6. Take 5 things out of your purse or car, or even off the ground if necessary, and arrange them on the floor. Ask the child to memorize the objects. When he says he's memorized them, ask him to turn away. Remove one of the objects. The child must guess which object is missing. Make this easier or more difficult by adding or subtracting objects, or, instead of removing objects, switch the places of two objects. While not terribly thrilling, it's a creative babysitting idea that at least give you something to do if you're stuck somewhere.
7. Hide-and-go-seek. Set the boundaries of where the child is allowed to go, and have at it. You may even elect to be "all-time-seeker" which children typically appreciate.
8. Create a treasure hunt, starting with one clue that leads to a spot with the next clue. Have some sort of prize at the end. Either instruct the kids on how to write the clues and lead the "seeker" from one spot to the next, or do that part yourself and let the kids seek the treasure.
9. Outside games ought to be easy enough, but if the children are bored with basketballs and baseballs, try building an obstacle course. You can use just about all of their outdoor toys for this creative babysitting idea, and the kids will get inventive with what tasks you have to do.
10. Got chalk? Kids still enjoy creating outlines of their bodies on the driveway. If that's too messy, opt for creating a 4-square game. You can even make just two big squares and play that way.