Arex was a member of a tripedal species[5] (given as "Edosians" in Alan Dean Foster's novelizations of the animated episodes, but as "Triexians" in Peter David's New Frontier series) and had three arms and legs.
Praetor Shinzon of Remus was able to obtain the disassembled B-4 and placed some special programming into him, so he could infiltrate the USS Enterprise-E to gain tactical information of the Federation from the ship.
B-4 briefly reappears in Star Trek: Picard where it's revealed that he was ultimately disassembled, but Doctors Altan Soong and Bruce Maddox had used the remnants of Data inside of his positronic network to build a new race of androids.
Projections (VOY)(recurring thereafter) While stationed aboard the USS Enterprise-E in 2373, and through a strange turn of events involving the Borg, Barclay was able to meet one of his idols, Zefram Cochrane.
[9] According to dialog in "Trials and Tribble-ations", Klingon intelligence subsequently turned its back on Darvin, who spent the next 100 years posing as a human merchant going by the name "Barry Waddle".