When the Titans are watching Sumo on a TV screen, there are 5 teenagers with their backs towards us and one is wearing a red jacket with a blue and pinkish pill on the back of it. This is Kaneda and his gang from the hit anime Akira (1988) by Katsuhiro Ôtomo.
The version of the Teen Titans theme that is sung by Beast Boy in the karaoke bar is a verbatim translation of the Japanese version of the song used during the original series.
During Beast Boy's karaoke scene (around 32m30s), part of the lyrics are "Earthquakes, Lightning, Fire...Dad." These are part of a cultural in-joke of sorts, in that these four are the things Japanese people fear the most, although not necessarily in the order listed in the song.
The home video releases have a bonus episode of Teen Titans (2003) called The Lost Episode (2005). This episode was originally an online exclusive as a promotion with Post Cereals that began running in January 2005. Specially marked boxes of Post Cereals provided consumers with a token code to log onto postopia.com and view the "Lost Episode." It's a short episode only 12 minutes long, regular episodes are usually 18-20 minutes long, which is probably another reason why the "Lost Episode" never made it to air.
Raven reveals that she can read six languages: English, German, Latin, Rumanian, Ancient Sumerian, and Sanskrit.