Characters
Now really, it's rude enough being alive when no one wants you, but showing up uninvited to a wedding?
— Lord Farquaad • Shrek

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker scornfully says that merely being alive when nobody wants you is impolite enough, before treating an uninvited appearance at a wedding as an even greater offence. The insult is theatrically snobbish, dismissing the intruder's very existence as a social imposition.
Context reviewed