Dual layer CDs are not a thing but yes you can put a 'half hour' episode on a CD at 3.5-4Mbps and it will look pretty good, better than the average streamed video.
And compared to the not-fully-compatible 99 minute CD-Rs, they only get an extra 50% space. Not a very impressive format there when burnable DVDs were already out and would obviously drop in price over time. Plus you could get another 14% by using mode 2 with reduced error correction...