Does Scooby know Snoopy? One might think so upon watching the debut episode of A Pup Named Scooby-Doo.

Here is a screenshot from that episode along side a screenshot from A Charlie Brown Christmas.

Notice how Fred and Daphne look as they yell, "Slow down, Velma, slow down!" They look like the Peanuts characters.

Could it be that Snoopy and the Gang grew up in Charlie Brown's community?

That would explain Scooby and Snoopy being seen together.