Falconcina

Falconcina is the het ship between Captain Falcon from the F-Zero fandom and Lucina from the Fire Emblem fandom.

Super Smash Bros. for Wii U and 3DS
Lucina and Captain Falcon were announced for Super Smash Bros. for Wii U and 3DS at the same time, alongside Robin. Captain Falcon was a veteran, Lucina was an "Echo Fighter" of Marth, before the term even existed.

In Lucina and Robin's reveal trailer, Lucina is fighting a losing battle against a mysterious opponent, which already left Chrom incapacitated. Before launching into another attack, she wonders what her opponent's power is, having never seen something like that before. It is then revealed that her opponent is none other than Captain Falcon, who flashes his eyes at her. Lucina looks back at the struggling Chrom and charges at Captain Falcon, grunting that her next attack is to avenge Chrom. She dodges a regular punch of Captain Falcon and then tries to stab him, only for him to block it nearly effortlessly. He then kicks her, knocking her off-guard and leaving her at the mercy of his Falcon Punch. But before he can finish saying it, another challenger approaches, distracting him. Said challenger is revealed to be Robin, who came to Lucina's rescue, managing to get Captain Falcon away from Lucina, but failing to put a single scratch on him. The trailer ends with Robin and Lucina still fighting Captain Falcon off-screen while Chrom laments that he'll get his chance another day, before passing out.

Super Smash Bros. Ultimate
The official character banner places Captain Falcon and Lucina close to each other. They appear to be dashing into the same direction.

Fanon
Falconcina has a decently sized following. Most fanworks of Falconcina depict Captain Falcon as regretful of his actions toward Lucina and wanting to make it up to her somehow. Whether through humorous antics or serious, dramatic confessions, Lucina accepts his proposals and the two gradually grow closer. Other fanwork depicts them as already being in a relationship.

People were really intrigued by Captain Falcon's appearance in Lucina's reveal trailer, arguing that it not only made him look like a complete badass, but also really helped illustrating the weirdness of Super Smash Bros. crossovers. It makes sense that Captain Falcon would be overpowered in a relatively grounded setting like Fire Emblem, thus seeing it portrayed in a trailer was not what people expected. People already started speculating what could've happened between Captain Falcon and Lucina that they would end up fighting each other in a way that could've potentially claimed Chrom's life. A number of people claim that Chrom taking Captain Falcon's hit was part of the plan to ensure that his daughter and Robin could join the roster, implying that Captain Falcon was testing the cast of Fire Emblem Awakening.

Though a number of memes have Captain Falcon team up with the two of them to dunk on Chrom, mocking him that he didn't make it in for the fourth game.

Fandom
FAN FICTION
 * Captain Falcon/Lucina on FanFiction.Net

Trivia

 * While small, Falconcina has some dedicated fanfiction authors for the ship, including Smash King24 and Rie Sonomura.