That's really cool, heralde!
"He was especially kind to kids visiting the set." And there's that one story Jerry told about Richard asking him to perform the Count for a group of kids - "Can you imagine the effect this has on a child's mind?"
Other actors, I imagine, would be annoyed at the presence of children on the set - but Richard, as we've seen time and time again, would immediately run over and give the kids a wholehearted welcome into the Muppet world. (and if the welcome involved spooking one of the adults, that made it all the more fun)
Like I said once, I'll bet that of the Muppet performers, Richard was one of the most popular with the children.