The Backyardigans is a computer-animated musical children's TV series created by Janice Burgess. The series was written and recorded at Nickelodeon Animation Studio.[7] It centers on five animal neighbors who imagine themselves on fantastic adventures in their backyard. Each episode is set to a different musical genre and features four songs, composed by Evan Lurie with lyrics by McPaul Smith. The Backyardigans' adventures span many different genres and settings. The show's writers took inspiration from action-adventure movies, and many episodes are parodies of movies

The HD Version has been seen in the Treehouse Brasil miniatures of Backyardigans, but as you can see the episodes are in bad quality, we can confirm that Nickelodeon or Treehouse Brasil have the HD Versions of Episodes 

Season 4 is released in HD, We need the Season 3, Season 2 and Season 1

Me and Backyardigans fans would be happy and excited to see again the series that marked the childhood of many people.