In the cartoon series "Dexter's Laboratory" what is the name of Dexter's rival and competitive boy genius?

"Dexter's Laboratory" is an American animated television series created by Genndy Tartakovsky for Cartoon Network and distributed by Warner Bros. Domestic Television. It follows Dexter, a short, enthusiastic boy-genius with a hidden science laboratory in his room full of inventions, which he keeps secret from his clueless parents, who are only referred to as "Mom" and "Dad".

Dexter has a bitter rivalry with his neighbor and classmate Mandark, a nefarious boy-genius who attempts to undermine Dexter at every single opportunity.

Rob Tartakovsky pitched the series to Fred Seibert's first animated shorts showcase "What a Cartoon!" at Hanna-Barbera, basing it on student films he produced at the California Institute of the Arts. Four pilots aired on Cartoon Network and TNT from 1995 to 1996. Viewer approval ratings led to a half-hour series, which consisted of two seasons totaling 52 episodes, airing from April 28, 1996, to June 15, 1998. On December 10, 1999, a television film titled "Dexter's Laboratory: Ego Trip" aired as the intended series finale.

In November 2000, the series was renewed for two seasons containing 26 total episodes, which began airing on November 18, 2001, and concluded on November 20, 2003. Due to Tartakovsky's departure, the last two seasons featured Chris Savino as showrunner along with a new production team at Cartoon Network Studio.