Hey, It's That Voice!: Inverted; Despite many people insisting otherwise, Janeane Garofalo is not the voice of Daria (it's Tracy Grandstaff, who also voiced Daria back when she was a supporting character on Beavis and Butthead) and Ms. Li is not voiced by Nora Dunn from Saturday Night Live, though Ms. Li does sound like Lydia Karaoke [the meddlesome network censor] from Histeria! (who actually is voiced by Nora Dunn). Nora Laudani — the actual voice actress for Ms. Li — appeared on Who Wants to Be a Millionaire? and did her Ms. Li voice to prove it.
Played straight with Wendy Hoopes, the voice of Jane (who played Mona Sax from Max Payne).
Within the show, she also played Helen and Quinn.
The Mexican Spanish dub has many regulars who dubbed Anime or another famous roles in the past:
Helen's Spanish VA is a very complex case: She was voiced by the same VA who voiced Luna and Bulma, but later she was replaced by the same VA who voiced Sailor Jupiter and Shampoo, but she died in a house accident, and her former VA voiced her again and later replaced again, this time with Sailor Mars's Spanish VA.
No Export for You: Unlike Beavis and Butthead, the series was dubbed in very few languages (and all of them from Western countries). Other countries only showed a subbed version (like South Korea and Israel) or never bothered to broadcast the series in first place (like Japan).
Talking to Himself: Many of the regular characters are voiced by the same actors & actresses:
The aforementioned Wendy Hoopes, who played Helen and Quinn Morgendorfer as well as Jane Lane.
According to the Daria Wiki, Jane is the closest to her normal speaking voice.
MarcThompson voiced Mr. Anthony DeMartino, Mr. Timothy O'Neill, Kevin Thompson, Jamie, and Charles "Upchuck" Ruttheimer III (during the first season only).
Janie Mertz voices Brittany Taylor, Sandi and Linda Griffin, and goth girl Andrea in her last two appearances ("Mart of Darkness" and "Is It College Yet?")