Olga "Lalavava" Astronomonov, also known as Lala Fafa, is the younger sister of Mandark and a one-time antagonist in Dexter's Laboratory. Mandark's sister is 8 years old and was the second in line of the evil children of the hippy pacifists - albeit she is the little-known one.
Like her brother Mandark, Lalavava was voiced by Eddie Deezen with a slightly high-pitched voice.
However, unlike DeeDee, she is not an quite so ditzy, and Mandark fears her. This is very similar to how Gaz is depicted on Invader ZIM. He shares some certain similarities with his younger sister, and they are both the opposites and rivals of Dexter and his sister, DeeDee, the latter of whom he is madly in love with. Lalavava and her brother, Mandark, look very similar, in contrast to Dexter and DeeDee.
Unlike their brothers, however, Lalavava and DeeDee end up becoming friends. DeeDee and Lalavava instead go to the mall while both agreeing that science is lame.