The "twist" for Hank McCoy in the Mutant X Universe was that his self-experiments mutated him differently than in Earth-616, and he eventually lost his intelligence. Accounts of the Brute's past were often contradictory, though. Mutant X #1 indicated that his loss of intelligence was relatively recent, after he mutated himself, the formation of the Six, and the construction of their Castle base, and #24 confirmed this.
The S.H.I.E.L.D. Files in the back of #1, however, indicated that McCoy lost his intelligence years earlier, when he left the X-Men to work for the Brand Corporation as he did in 616, in the same experiment that mutated him from his original appearance.
Furthermore, #22 showed the Brute confronted by the original Hank McCoy and a blue-furred Beast similar to 616, indicating he had THAT appearance for a time as well.