Went to a wedding where the couple hadn't rehearsed their vows before the ceremony. Unless you're making up your own vows, you don't really have to study them ahead of time because a) the priest prompts you with each phrase, and b) you know how they're going to go, "in health and in sickness", etc.

Until the priest prompts the groom, "God's holy ordinance". And you could tell the groom's thought processes went something like:

yadda yadda
"God's Holy Ordinance"
Thought 1: WTF?!? Belt-fed weaponry?
Thought 2: Oh Right... The Holy Hand Grenade of Antioch... always useful in a wedding
Thought 3: Oh crap... Don't laugh
"God's ... ah ... Holy Ordinance"