"We're Dancing" is a song that was written for the unaired episode "The Lazy Dance". It is a variation of the Icelandic song "Dönsum", created in the early 2000s. It was not fully featured in any episode; however, "Miss Roberta" uses a short clip of the song and "Dancing Duel" features the instrumental.
The only official release of the song as an audio track was on Nick Jr. Radio, where the mp3 is currently available. The song is listed as "Dancing" on the site.
It's easy as can be.