This isn't a terribly funny joke, or even mildly funny, but it isn't a repost.... So it's okay.

Two missionaries in Africa were apprehended by a tribe of very hostile cannibals who put them in a large pot of water, built a huge fire under it, and left them there.
A few minutes later, one of the missionaries started to laugh uncontrollably.

The other missionary couldn't believe it! He said, ''What's wrong with you? We're being boiled alive! They're gonna eat us! What could possibly be funny at a time like this?''

The other missionary replied, ''I just peed in the soup!''