Season six, Episode 233, "Rascals"
no, but there was a crossover in a comic book
It was in the episode "Hide and Q."
In the Star Trek: The Next Generation episode Unification I, Spock's father Sarek dies at the age of 203.(Although Mark Lenard appeared as Sarek in only one episode of the original series, he ended up reprising the role of Sarek six more times:as the voice of Sarek in the animated series episode Yesteryear,in the movie Star Trek III: The Search for Spock,in the movie Star Trek IV: The Voyage Home,in the movie Star Trek VI: The Undiscovered Country,in the Star Trek: The Next Generation episode Sarek, andin the ST:TNG episode Unification I.)
DeForest Kelley played Dr. McCoy on ST:TOS.
I think it was the "Contagion" episode where the USS Yamato was lost due to an 'Anti-matter' containment field failure .
no, but there was a crossover in a comic book
It was in the episode "Hide and Q."
colfoy
It is a season four episode entitled "Half a Life."
In Theory
Season 3 Episode 19
Mick Fleetwood played an unnamed Antedian, a fish-like alien, in the next generation episode "Manhunt".
Whoopi Goldberg first appeared in Star Trek with the 1988 Star Trek: The Next Generation episode "The Child".
"The Child", aired November 21, 1988.
That was "The Game", episode 105, fifth season.
Yes, it is.
It's Borgs from Star Trek the next generation episode "The best of both worlds"