Alice and Bob are going into an Arranged Marriage. They aren't marrying for love, but for their families' interests.
Alice and Bob come from a culture where a short courtship is common.
Either Alice or Bob (or even both!) doesn't have much time left to live, and they desire to know how it would have felt to have been married before dying. All in all, it would be extremely heartless to deny that Last Request, and the surviving part would be "free" to carry on his their life after the other's death. ("till death do us apart", after all)
Lampshaded: "Alice and Bob together forever...ALREADY?!"
Invoked: Bob proposes to Alice on their four-week anniversary...and Alice accepts.
Defied: Neither Alice nor Bob will even so much as discuss marriage until they've been together exclusively for at least a year, believing that a Fourth Date Marriage will not be a healthy or happy one.
"You think they'll last?" "It's hard to say...they haven't known each other that long..."
Conversed: "Wait, those characters just met! Why make them marry now?"
Deconstructed: Because Alice and Bob haven't known each other that long, their differences can cause problems. And what happens when the chemistry/butterflies/shiawase bubbles wear off? The marriage doesn't have a solid foundation, so it's a crapshoot whether or not it'll actually work out.
Reconstructed: Alice and Bob learn to compromise and work out their conflicts in a healthy manner. They also remember what's attractive about each other, even when Bob skips shaving for a day or two, and even when Alice is "retaining water." As a result, their hasty marriage is as healthy as (or healthier than) that of couples that dated for years before tying the knot.
Played For Drama: All the getting-to-know-each-other they have to do puts strain on Alice and Bob, both as individuals and as a couple. Can they get through it, and become stronger both as individuals and a couple? Or will they get divorced as quickly as they got married.
Back to Fourth Date Marriage and by the way, congrats on the great spouse! Wait—you've known them for how long?