Complex sentence: He also made brief cameo's in the two semi unnofficial sequels written by O'Brien's daughter Jane Leslie Conly, and also made a rather unfortunate appearance in the animated sequel to the first film as the main antagonist.
Split into simpler sentences: He also made brief cameos in the two semi unofficial sequels written by O'Brien's daughter Jane Leslie Conly. Finally, he made an appearance in the animated sequel to the first film as the main antagonist.