There is also a great project on Reddit, "RemasteringTMNT2003" which has painstakingly remastered the entire series in 1080p. It's not perfect - you get a glimpse of moments that are a little fuzzy or which don't look quite right - but overall, the result is spectacular! A great way to get into the series.

https://www.reddit.com/r/RemasteringTMNT2003/