Robin and Cyborg's competitive friendship is also evident in Divide and Conquer (2003) and Winner Take All (2004).
Beast Boy's sadness at Cyborg leaving brought to mind their strong friendship in the comic book series; Beast Boy and Cyborg have been best friends for a long time in the comics.
Bumblebee's ability to resist Brother Blood is consistent with the comments she made in Wavelength (2004). With Blood's amped brain power, she is unable to resist as strongly in this episode.
In the comics, Brother Blood kidnapped and brainwashed Dick Grayson and Raven and turned them against their teammates in "The New Teen Titans" (vol. 2) #26-31. They broke his control and exposed Blood as a fraud.
SPIOLER: After two seasons where Slade was trying to make someone like him, the creative team thought it would be an interesting contrast to have a bad guy who was trying to make himself more like the hero. They decided to make Brother Blood try to make himself look like Cyborg. Plus, the liked the idea that Brother Blood would voluntarily do to himself something that happened to Cyborg as a result of an accident because it made him extremely creepy.