There is no particular easter egg to see here, however the explanation to it can be found here:
On the second floor of the castle, affixed to the wall adjoining the steps that lead to the door that requires 50 Power Stars to enter, is a plaque that reads:
"Shhh! Please walk quietly in the hallway!"
Possibly answered in the remake, where Toad says this to Wario:
"Wario, it's impolite to shuffle noisily around the castle, you know. No matter how tough you look... it's...umm...prohibited."
While that doesn't explain much, maybe he was referring to the sign as justification to complain about Wario's behaviour here, so it's given a sort of mysterious, new reason to exist in the remake/Mario 64 DS.
Taken from Chrisjh0223 from http://www.gamefaqs.com/boards/198848-super-mario-64/44157242?page=10