At one point in Mario & Luigi: Brothership, Bowser Jr. announces an extremely large coin reward for catching Mario and Luigi, which appears to be simply a random number to Western audiences.
However, this is actually intended to be a pun using goroawase, a type of Japanese phonetic matching, to sound like a sentence when spoken aloud. Different digits each have several ways they can be pronounced for the purposes of goroawase, but with a certain pronunciation, the number spells out "Bowser is the best".