Project Serpo has been a thing in the USA since around 1965. There's no reference in the (quasi)-real world to the kind of slug-like aliens seen on the cartoon or in the comics, but it involved Zeta Reticuli, which is a real star system, like many other close encounters of the time, such as the Barney and Betty Hill case, which is yet to feature in the comics or cartoons. The aliens involved where very similar to the Communion-style greys. In fact, there's a scene in the Spielburg movie, "Close Encounters of the Third Kind" that involved astronauts and other returnees that bore a resemblence to the participants in Serpo lore...
