As brilliantly observed by Monty Python, there is no creature more dangerous than an intelligent sheep...
(A tourist approaches a shepherd. The sounds of sheep and the outdoors are heard.)
Tourist (Terry Jones: Good afternoon.
Shepherd (Graham Chapman): Afternoon
Tourist: Ah, lovely day isn't it?
Shepherd: Ar, 'tis that.
Tourist: Are you here on holiday or...?
Shepherd: No, no, I live 'ere.
Tourist: Oh, jolly good. I say, those ARE sheep aren't they?
Shepherd: Yeh.
Tourist: Yes yes, I though so. Only, why are they up in the trees?
Shepherd: A fair question and one that in recent weeks 'as been much on my mind. It's my considered opinion that they're nestin'.
Tourist: Nesting?
Shepherd: Aye.
Tourist: Like birds?
Shepherd: Exactly. Birds is the key to the whole problem. It's my belief that these sheep are laborin' under the misapprehension that they're birds. Observe their behavior. Take for a start the sheeps' tendency to 'op about the field on their back legs. Now witness their attmpts to fly from tree to tree. Notice that they do not so much fly as... plummet. (Baaa baaa... flap flap... thud.) Observe for example that ewe in that oak tree. She is clearly trying to teach her lamb to fly. (baaaaa... thud) Talk about the blind leading the blind.
Tourist: Yes, but why do they think they're birds?
Shepherd: Another fair question. One thing is for sure, the sheep is not a creature of the air. They have enormous difficulty in the comparatively simple act of perchin'. (Baaa baaa... flap flap... thud.) As you see. As for flight its body is totally unadapted to the problems of aviation. Trouble is, sheep are very dim. Once they get an idea in their 'eads, there's no shiftin' it.
Tourist: But where did they get the idea from?
Shepherd: From Harold. He's that sheep over there under the elm. He's that most dangerous of animals, a clever sheep. He's the ring leader. He has realized that a sheep's life consists of standin' around for a few months and then bein' eaten. And that's a depressing prospect for an ambitious sheep. He's patently hit on the idea of escape.
Tourist: Well why don't you just get rid of Harold?
Shepherd: Because of the enormous commercial possibilities should he succeed.
Voice Over (Eric Idle): And what exactly are the commercial possibilities of ovine aviation?