At first, Mia's line "and when faced with tribulation, I think of my own inspiration./He taught me to always hold my stance" in the song Justice for All seems to be just a line they put in to make a rhyme and give Phoenix the chance to make a callback in the reprise... then you realize that she's singing about Diego Armando.
Edgeworth's defense of Cody in The Samurai Always Wins makes a lot more sense when you consider the fact that Edgeworth was involved in a murder case and may have had to testify when he was Cody's age.
In 600,000 Volts, von Karma sings "Now your life's depending/On giving that letter to me" when he tries to threaten Phoenix and Maya into handing over their evidence. It might seem like just a way to intimidate them but then, remember that he did already kill a defense attorney who defied him. Makes you wonder what would have happened if the tazer didn't just knock the two of them out...