Apparently, the Game Boy Advance can now play feature-length movies without the additional movie player. Where have I been? From the article: “[The GBA] has been capable of playing movies with the GBA Movie Player for some time. However, it often requires a lot of technical knowledge, and extra hardware. But Majesco now also provides full-length movies on the GBA, and it doesn’t require any additional hardware to play.”
Regarding the quality of the feature-length films the author writes: “If you’re paranoid about the quality of your video, then playing it on the GBA is probably never going to be your thing. However, it works, and after a few seconds you stop noticing the quality of the video and simply enjoy the movie.”
Official Majesco GBA Video Site 
[Source: About]