The best stories often combine unlikely elements. A literate spider and a pig? A British boarding school and a wizard? An African gray parrot and a girl with leukemia? (That last idea is from my book, The Desperate Adventures of Zeno and Alya.) When people ask me how I get my ideas, I answer, I combine images that don't belong together.
To make a connection between two things that DON'T go together, you have to think deeply and uniquely. You have use a lot of imagination to bridge the gap. The tension between the ideas will add to the magic.
Here's the prompt. Collect an assortment of pictures from magazines. Pick ones that grab your attention. Then randomly select two or three of the pictures.
If they fit together, like the dragon and the princess bride, or the rescue dogs and the person lost in the maze, put one picture back and pick again.
What can you make out of a person hanging from a tree and the space station? Rescue dogs and electric guitars? Pillow-head people and a dragon?
As a variation, try separating your pictures into characters and settings. Go against the obvious choices. Try using landscapes to define your characters and people to conjure up new settings.
In this way, you'll leave your comfort zone and think outside the box. And you won't rely on cliches like those expressions! You'll come up with new ideas and images.