Though there are some outlandish conspiracy theories circulating on the topic, the presence of feral, or at least not fully domesticated, cats in Disneyland is a verifiable phenomenon that can be observed through photographic evidence, which shows that these felines hang out in the park during the day and not just at night. An article from Vice indicates that Disneyland is well aware of these cats, and that the park has hired animal rescue organizations to perform spay and neuter operations on these cats. The cats provide a helpful, free service at the park, helping to keep rodent populations from growing out of control.
Disneyland officials seem to have fully embraced the feline presence in the park, but they seem hesitant to make official statements about their unofficial, non-human pest control staff. Still, park visitors frequently photograph the cats.
There is a certain amount of public fascination with the Disneyland cats. Actor Ryan Gosling, a former Mouseketeer, has spoken publicly about his apparent belief that Disney breeds these cats with special abilities, making them into "commandos" that patrol the park. There's no indication that this exact scenario is true, but the presence of the cats is certainly easy to confirm with a simple visit or online image search.