The further and darker adventures of Batman with a new Robin, a closer association with Batgirl and the previous Robin now as Nightwing.
The Riddler only has one line in the series. "Hey diddle diddle, time for a riddle!" Though technically, he has 2 in the series, but the 2nd line is shared with another character in which he simply chants "Yeah!" After Harley Quinn says "We demand money!". He shares this line with Scarface. Although in a crossover with Superman, he is seen teamed with Bane and Mad Hatter. Even then though, he doesn't say more than 3 lines.
Robin:
It's your kind of show, Puke face: a double feature.
Although this show goes by "Batman: The Animated Series Volume 4" on video, the original intro from "The New Batman/Superman Adventures" can be seen as a bonus feature if the viewer selects "Play All" on the DVD's main menu, in addition to the original BTAS intro.
English