Upon his return to AAA in 2008, X-Pac announced he would be forming a new group, D-Generation-MEX. X-Pac formed the group after returning to AAA and turning on Konnan's Legión Extranjera. Pac declared Mexican citizenship after being in AAA and living in Mexico for over a year.
The group has been presented as close to X-Pac's previous WWE Degenration X group as possible; they use the same green and black theme, a similar(but different) entrance video, and the same entrance music as the WWE group. D-Generation MEX also uses the catchphrases and body gestures as DX. The group claims to be neither rudos or tecnicos, though their actions are close to other AAA rudo groups.
X-Pac had briefly been announced as working for CMLL before making this appearance, which started a pattern of members being surprise jumps from the rival promotion, much like X-Pac had done when joining DX in 1997.
The first to join him would be Rocky Romero, who before joining AAA had been working in rival CMLL as the masked Grey Shadow. He debuted in AAA as the Grey Shadow only to take the mask off himself after beating up Los Bello Stones and La Hermandad. X-Pac and Romero teased there'd be two more members to come.
The following week, they were joined by another jump from CMLL to AAA, as the Russian técnico Alex Koslov made the move & joined the group.
At the 2009 Rey de Reyes, Juventud Guerrera jumped to AAA and appeared to join the group on the live show, but the members of the group didn't want him involved and he was never made a member on television. Marco Corleone teamed with the group at times, but did not appear to be an official member.