The Numberblobs challenge Twenty to a singing count-off.
Twenty is challenged by the Numberblobs to count to Twenty. A song ensues about counting to Twenty in different ways.
Halfway into the song, Three tries to get her own lyrics, but is disrupted by Four and Five. After their turn, she attempts to count to Twenty, but is exactly one off... but she does create someone else: Twenty-One! Twenty eventually challenges others to count to Twenty-One, as the song ends.
This episode mentioned an upcoming Numberblock, Twenty-One.
This episode introduces Numberfeet (used to count 11-20).
Just like Numberblobs, the song starts when the episode starts.
A leaked picture from this episode went viral on Twitter. When someone asked the Twitter account of Numberblocks about the picture, they said it was just the Numberblocks rehearsing for the new episodes of Season 4.