You can buy a kit for that. It's got a clear plastic tray that fits over the bowl and under the seat. I gather you sprinkle some litter in it, and over time you use less litter until the cat gets used to seeing the water through the plastic, then you remove the tray. Some friends of my parents had a Siamese who used to flush the toilet in their apartment to watch the water swirl around when he was bored. They always threatened to teach him to use the commode because he already flushed anyway . . .
In gallery 4, that is one big cat, but the rug she's standing on makes her look bigger. At least, I think she's standing on a small brownish rug, but my track record interpreting photos isn't too good lately . . .