Beatbox Showdown is a song performed by Robin and Kid Flash in "Multiple Trick Pony". It was a battle of the tongues, as Robin was proving his worth to Kid Flash, exhibiting his skill in beat boxing, only for Kid Flash to join in as well.
Robin: Can you beatbox like this? (makes various sounds with his mouth.)
Kid Flash: Woah, Woah (makes various sounds with his mouth.)
Robin: (makes various sounds with mouth)