“The dream dreams the dreamer”: Birthright, Part 1 (TNG) vs. Tinker Tenor Doctor Spy (VOY)

Data learns to dream, and the Doctor learns to daydream.

“A little ship that took a little trip”: The Terratin Incident (TAS) vs. One Little Ship (DS9)

Honey, I Shrunk the Crew of the Enterprise (and a Runabout)

“It is you who are not real, sir”: The Big Goodbye (TNG) vs. Badda-Bing, Badda-Bang (DS9)

An early episode of The Next Generation starts a Trek tradition of holodeck malfunctions, while a late-series episode of Deep Space 9 lets the crew use the holodeck exactly as its designers probably intended: to pull holographic casino heists.

“I Love Lucy is on tonight”: Little Green Men (DS9) vs. Carbon Creek (ENT)

We see Earth through the eyes of 3 Ferengi in the 40s, and 3 Vulcans in the 50s.

“I’m a doctor, not an historian”: The Trouble with Tribbles (TOS) vs. Trials and Tribble-ations (DS9)

The Original Series gives us a comedic classic, and Deep Space Nine pays tribble-ute with a comedic classic of its own.

“You people certainly have interesting problems”: Tomorrow is Yesterday (TOS) vs Future’s End (VOY)

Kirk and Janeway try to preserve the timeline – more or less – when they’re each thrown back to the 20th century.