Bad Export for You: The Famicom version of Contra made use of a custom-made mapper chip (the VRC II) that allowed for the addition of cut-scenes and a map display between stages, as well as animated backgrounds (such as moving palm trees in Stage 1 or falling snowflakes in Stage 5). The NES version, which was released on a standard UNROM mapper (since Nintendo produced all the NES cartridges released in America), lacked all these graphical effects.
Name's the Same: Browny (a.k.a. CX-1-DA-300 Combat Robo) from Hard Corps and Brownie (a.k.a. BR-W9) from ReBirth.
While Brownie's design is obviously based on Browny's, her name is simply Tsugu-Min in the Japanese version.
While there's obviously no physical resemblance (even with his multiple transformations depending on which path you take), Colonel Bahamut is bound to remind most Final Fantasy fans of the summonable dragon that shares his name. Since they're both named after a big fish from Arabic mythology.
No Export for You: Contra Force was only released in North America, even though its Famicom counterpart (Arc Hound) was canceled.
The Appaloosa-made titles, Contra: Legacy of War and C: The Contra Adventure, were never released in Japan either. Also, Contra Adventure never came out in Europe, even though Legacy of War did.
The MSX2 version of Contra was only released in Japan and did not have an official release in Europe, even though Nemesis (aka Gradius), Vampire Killer (the MSX2 equivalent of the first Castlevania) and Metal Gear were all released there. However, many ROM sites incorrectly list the game under the title of Gryzor (the European name of the first arcade game).
Port Overdosed: The original game, whether as Contra or Gryzornote or Probotector, is one of Konami's most widespread games, being released on several platforms in the 80s and re-released many times since then.