Star Trek The Next Generation: S6-E4 - "Relics" is on, on BBC
Probably the best 'Crossover' episode ever, of any series.
James Doohan (Montgomery Scott - Scotty) and a Dyson Shere - circa Oct, 1992.
You can't get better than that.
Edit: the best line in the episode ?
Scotty finds out about synthahol.
"Synthetic Scotch, Synthetic Commanders" (Referring to Data)
Heh, heh, heh.
Best part of the episode:
When Scotty walks onto the Holodeck of the Constitution Class Enterprise, Picard joins him. (Wait for it)
After a bit of discussion...
Scotty: "Old girlfriends we'll never meet again."