Mostly, kids are taught that mammals do not lay eggs and give birth to live young. Throw that idea out the window. Well, okay, not completely, there are only a select few animals that go against that idea. The platypus is part of a small family called Monotremata, and there are only five of them. There are platypuses and five species of spiny anteaters called echidnas. Sadly, they are all only found in New Guinea and Australia natively. They share a lot of features with other mammals but also lay eggs. In the late 1700s, before Colonel David Collins wrote his book, An Account of the English Colony in South Wales, the only information Europe had on platypuses was a drawing and the skin of one. The Natural History Museum writes, “Some suspected the strange animal was a hoax - perhaps a taxidermy construction of a duck's bill attached to the body of a mole.” So Europe saw the animal and thought it was so strange that it could not be real. Now we know that they are very real, and they are listed as a near-threatened species. 

For quite a while, there were not a lot of famous platypuses, real or fictional. People knew of their existence because, of course, such a strange animal would make itself known. Until 2007, when Phineas and Ferb aired, including the family pet leading every episode's B-plot, Perry the Platypus. In case you do not know Perry, he is the teal-furred, yellow-beaked family pet of the Flynn-Fletcher family living a double life as Agent P. of O.W.C.A, (Organization With a Cool Acronym). Perry’s original name was Bartholomew, and later changed to Perry by his family. He is about two feet tall, has been shown to understand both English and French and is musically inclined. Perry can, canonically, play bass guitar, guitar, can DJ, opera sing, and read sheet music. Perry is a male platypus, but he does not have his ankle barbs. At least not animated, they are only mentioned and used once in the entire show. In episode eight of season four, Doofemschritz hires an Australian platypus hunter, Liam, to trap Perry in the town's botanical garden. His backstory is interesting and a little silly, but Liam’s platypus hunting gear includes his own venomous ankle barbs. While chasing Perry, the Phineas and Ferb Wiki  for said episode’s transcript says, “Liam grabs Perry’s tail, but lets go when Perry swipes him across the face with his ankle barb.” It is likely the only frame where Perry’s ankle barb is animated. Sadly, because the entire show takes place in summer, and the mating season ends in March, Perry never produces his venom during the run of the show and can never use it.