Based on common episode guides, Season 4, Episode 4 is most likely one of the following:

The series has seen a resurgence on platforms like TikTok , where clips of Balthazar’s inventions are frequently shared.

In some databases like IMDb , this episode (where Balthazar invents a flying tram for his friend) is indexed differently but sometimes appears in lists for later seasons.

You can often find episodes of the animated series on platforms like JustWatch or Plex.