I've had this headcanon for a while, but I've never really told anyone other than my roommate. It involves the movie Labyrinth, the one from 1986 and has David Bowie and goblins and the awesomeness that is Jim Henson's imagination.
The idea is: how the Labyrinth works.
The Labyrinth is constantly changing, but that's rather obvious. Is it alive? Maybe. But how does it know what to change, where and how?
The answer is very simple: The Labyrinth adjusts itself to whomever is trying to solve it.
See, in my mind, Sarah did not simply solve the Labyrinth JUST because she needed to save Toby. No, there was more than one reason. She needed to grow up: In other words, she had to learn how to make friends, how to take responsibilities, and how to think things out to solve problems, like adults do.
These problems then manifested themselves into the various characters she met in the Labyrinth. The characters were always there, but the Labyrinth created the circumstances required for them to meet.
First, there was Hoggle. Sarah had to meet him outside the Labyrinth, where he was exterminating fairies. I believe the Labyrinth, shortly before (probably right as Sarah made her wish), the Labyrinth had created a fairy outbreak, and Hoggle was simply doing his job, preventing more from coming in. By making him work outside the walls, Sarah would meet him, and the seeds of friendship would be planted, though it wouldn't have sprouted unless the Labyrinth placed the idea in Jareth's head (or Jareth planned it all along) to have Hoggle be the one to guide people out of the oubliettes and back to the beginning.
Next she met Ludo. The creatures that are seen torturing him upon his arrival into the story are likely to be either lowly guards or amateur hunters. I'm assuming the former, for this reason: we see a guard wandering around the hedge-maze portion while Hoggle and Sarah are talking about them being friends. A Labyrinth's main purpose, other than housing monsters, is to keep unwanted people away from the goal at the center. After being aware of Hoggle's betrayal (I highly doubt he believed Hoggle's story in the first place), he likely sent out guards to bring Sarah back to the beginning if she was caught. The movie also shows that goblins are not the brightest bunch, so maybe these lowly guards only understood the "long brown hair" portion of Jareth's description of who to capture, and they caught Ludo instead. Because of this, Sarah was now able to meet Ludo.
Lastly, she met Sir Didymus. As much as I would like to believe his meeting was purely coincidental, there must be a reason, if my theory is to be precise. If this fox/dog hybrid is to be believed of his own words, then he has a highly developed sense of smell, however, his opinions on the matter are different from a normal person's, or he's been living in the bog for so long that he became accustomed to the smell. How Didymus got there is not important. What does matter is how Sarah got there. The Labyrinth intentionally led Sarah to the Fireys, who happened to be closest to the bog, knowing that Hoggle would save her through the power of friendship. Whether or not she did kiss him wouldn't have changed the result of the duo falling to the Bog of Eternal Stench. There was likely a trigger close by (seriously, who puts a castle wall right outside of a swamp and doesn't have a few safety precautions such as trap doors?) Same thing for when Ludo fell and suddenly reappeared to meet them in the Bog.
The Labyrinth knew what it was doing.