Pretty much as per subject. (And if he also does so in previous games or the 3DS version, sorry.) When you select 8-Player Smash, he says, "Eight-player Smash!" but when you pick regular Smash mode, he says what sounds like "Rainfall!"
I thought this might be a muddled way of saying "Ready to fight!" but he says this when the character screen pops up, before everyone is necessarily ready.