more of the dry humour we practice at work:

[after seeing a horse amongst a herd of cows]
dil: that's a funny looking cow there.
len: it's a horse.
dil: well... yes. but i was trying to be funny.
len: ah.
[later, passing the same field again]
dil: i still reckon that's a funny looking cow.
len: yes, i do believe you're right. seems to have a longer tail than all the others. more fluffy, like.
dil: indeed. i reckon it's a depressed cow, tho.
len: how'd you figure?
dil: well it's thin, so it can't be eating right, and look at it's long face!
[after a few seconds of pondering]
dil: continuing this joke after it failed so horribly the first time really isn't working, is it.
len: no. not really.
dil: thought so. [and stops]

[talking about the agency guy we had today]
len: looks like he's gonna be asleep soon.
dil: you're assuming that he's actually awake.
len: ah yes. my mistake.