Depending on how much you liked Newsies, there's four examples of this trope for you, since four of the season one cast members were in it: Dominic Lucero, Ivan Dudynsky, David Sidoni, and Mark David. Although, for some, those four are the entire reason they started watching the show, which may turn it into a Just Here for Godzilla. (Michael Jackson fans might also remember Lucero as one of the dancers from Jackson's Bad World Tour.)
Jennifer Cihi performed the theme song and joined the cast in the third season. She is also known for performing songs and being the singing voice of Sailor Moon for the English soundtracks.
Keep Circulating the Tapes: Good luck finding ANYTHING from this show. If you find a collection somewhere, please let the rest of us know!
The entire first season has been uploaded to YouTube by various people, as well as episodes from seasons 2, 3, and 4. It just takes digging.
Which may have been the point. There's a good chance that the producers were going for Stylistic Suck, giving it a "bunch of friends putting on a show in their trainyard" feel.
Actually, the show was Nickelodeon's most expensive to produce at the time, because of the complexity and specialization of the props, even if they were made of cardboard. Most of them, cardboard televisions aside, couldn't be used for more than one episode, as props were typically specific to an episode. Occasionally, things like a hat with socks on it for dog ears will pop up in multiple episodes (the Abusement Park and School Play episodes, for example), but most of the time, props were too specific to use more than once.
Screwed by the Network: Not exactly, but Nickelodeon pretty much hated the show. Roundhouse's writers narrowly avoided getting screwed in the early seasons, with Nickelodeon supposedly preferring certain cast members over others and getting sketches cut that the writers wanted kept in. (They ended up moving production out to California to apparently avoid more of this. Still got screwed in the end.)