Basic Trope: A couple decides to marry their way at the last minute.
Alice and Bob have a big white wedding planned, but elope at the last minute.
Alice and Bob are planning to elope, but then decide to have a bigger wedding so their families and friends can be part of it.
Alice and Bob bring the entire wedding with them through a drive-thru chapel in Las Vegas.
Alice and Bob throw together a $30,000 fancy wedding in a week's time
Alice and Bob have a big white wedding planned, but decide to downsize a couple months before their wedding day.
Alice and Bob are planning to elope, but then decide to have a party in their back yard for their friends and family.
Alice and Bob got frustrated with wedding planning for various reasons (finances, contracts, meddlesome relatives), or never wanted a big wedding in the first place
Alice and Bob decided they didn't want to alienate family members and friends
One of them has cancer and they aren't sure how things are going to be, so they have a civil ceremony at the courthouse for themselves and have the big fancy dream wedding if and when things get better.
Alice and Bob wanted to have a destination wedding, but knew a lot of their families and friends wouldn't be able to afford the trip, so they are having a separate reception for that social circle when they return or on their anniversary.
Alice and Bob had a civil ceremony, but then religion became important to them later, so they decided to renew their vows in a religious setting.
Alice and Bob went to the courthouse, but are planning to have a big party later (maybe with a vow renewal, maybe not), probably on an anniversary, when they have more money.
All decked out in their wedding regalia, Alice and Bob stop at a drive-thru chapel (also a fast-food joint) and get married...as well as order fast food.
In a Good Angel, Bad Angel situation relating to wedding stress, while Alice debates whether she and Bob should go ahead with the with the Vegas wedding or get their families involved, the Good and Bad angels on Alice's shoulder skip to Las Vegas and get married.