In Brawl we had Snake's codec calls; today we have Palutena's Guidance.
If you play as Pit in Super Smash Bros Wii U -- out November 21 -- you'll see a lot of hidden conversations between him, Palutena, and the nature goddess Viridi. Many of them are useful, and some are kind of hilarious.
The fine folks at GameXplain have compiled all of the secret messages you can find in the game, and some of them are amazing. ("No point in having two characters that are pretty much carbon copies. Am I right?")
Watch them all here: