In the episode Roborapper the song Kickin' in The Beat contains an extra rap verse from the one-shot character, Flap.
Lyrics[]
<poem> Flap on the back for real No more Roborapper Free-bros show me the light So now I join the fight Mantyz, run for cover Freefonix gained a brother Attitude you don't know of Straight from the heart Looking out for each other