Get out your season seven DVD (which should be lovingly stored in a safe climate controlled place like my M*A*S*H DVDs) and take a look at the opening scene of "Peace On Us."

As the camp assembles after a wild night of partying, keep your eyes out for Klinger, who is already standing in the compound smoking a stogie.
It's not Jamie Farr playing Klinger!
As the scene continues, there are a few shots of Kilinger bickering with Winchester, but all of those shots take place on the indoor M*A*S*H set!

At the end of the scene, when everyone is dismissed, look again at Klinger. It's not Jamie Farr - again!

It's a conspiracy I tell you.

Hmm...

The truth is out there!

What gave it away? The nose?

If you look at the episode, Klinger is barely in it. He's not even at the big party scene at the end where everyone is dressed in red.
My guess is that Jamie Farr wasn't available or something, so they did a few shots with Jamie Farr on the interior camp set, and inserted them in the episode.

That is too funny :)

That is Very Funny