There are around 10,000 saints officially recognized by the Catholic Church. That may seem like a lot, but it's actually a very exclusive club. In order to be officially canonized by the Vatican, one must have lived a life of extraordinary virtue and service, and performed at least two miracles (sometimes posthumously). Supernatural acts have always been hard to come by and harder to authenticate, and even then sainthood isn't assured. For instance, in 13th century France, loyal and selfless Guinefort of Lyon was said to have healed infants after his death. His village swore by his holiness. The Church condemned this practice as demon-worship and superstition.
Problem was, Guinefort was a dog.
As the story goes, Guinefort was a greyhound owned by a local knight with a newborn son. When the knight left to go hunting, the dog was left to watch over the baby. While it may have been a more sensible idea to have a neighbor do this, it speaks to level of trust between master and dog. One day, after returning from the forest, the knight was horrified to find his son missing and Guinefort soaked in blood. Thinking that the dog had eaten his child, the knight hacked Guinefort to pieces. This proved to be a tragic error, as once the knight had finished he heard the cries of his son from beneath an overturned crib. The child was unharmed and nearby the knight discovered the body of a viper. Guinefort had killed the snake to protect the baby and was rewarded for his heroism with death.
Mourning the loss of his dog, the knight threw the body down a well and planted trees in Guinefort's honor. Soon news of this brave animal reached the village, and the commoners arrived to pay tribute. Some brought their children to be blessed, and Guinefort was ultimately venerated as a community saint; his watery grave rebuilt into a shrine. 13th century scholar Stephen of Bourbon wrote of Guinefort and his worshippers in disparaging terms, alluding to sacrifice and unholy pacts. After this bit of bad press, the Church prohibited Guinefort idolatry, and yet the cult endured as late as the 1930's before dying out.
Would you like to know more?
-Read Stephen of Bourbon's original account of Saint Guinefort