♪ If it's one, it's a carrot!
They're singing a song called Ippon Demo Ninjin. It's supposed to teach children about numbers and counters.
In this case, 本（ほん）→ Counter for long things (carrots, pens, etc.). ♪ If there's two, they're sandals!
足（そく）→ Counter for pairs of shoes or socks. ♪ If there's three, they're yachts!
そう → Counter for small boats. ♪ If there's four, they're sesame seeds!
粒 tsubu, very small things like grain or seeds.
Don't "?" me.
No, no. I was trying to make a joke with five and "roku"... Was trying to go with the flow of the song, you see.
♪ If there's five, it's a rokurokubi!
A very clever pun here.
五 (go) means five and rokurokubi being what Sekibanki is.
