One example of funny wedding advice is for the speaker to warn the bride her husband won't change and to warn the husband that his wife will. One sweet and amusing bit of advice is to tell the bride because the groom stole her heart, she should steal his name.
The speaker can also warn the groom that marriage is an ongoing relationship in which one of the two is always correct and the other one is a husband.
Some funny advice is suitable for both bride and groom, such as the speaker telling them that marriage is less about the two of them looking at one another and more about the two of them both looking in the same direction. The speaker can also remind the two of them that one of the reasons they are in love is that they both hate the same things.
Some advice that is both funny and poignant is that happiness in marriage is not about having everything the two of them wants but making the best out of everything they have.
Lighter funny advice for the speaker to give is to tell the newlyweds that they may now update their Facebook statuses and that they should both be happy that they have found the one person they want to annoy for the rest of their lives.