"Angus Broon of Glasgow comes" joke

Angus Broon of Glasgow comes to the little lady of the house, exclaiming,
"Maggie, cud ya be sewin on a wee button that's come off of me fly? I can't
button me pants."
"Oh, Angus...I've got me hands in the dishpan, go up the stairs and see if
Mrs. MacDonald could be helpin ya with it."
About 5 minutes later, there's a terrible crash, a bang, a bit of yelling
and the sound of a body falling down the stairs. Walking back in the door
with a blackened eye and a bloody nose comes Angus.
The little lady looks at him and says "My God, what in hell's name happened
to you? Did you ask her like I told you?"
"Aye," says Angus. "I asked her to sew on the wee button an she did.
Everything was goin fine, but when she bent doon to bite off the wee
thread, Mr. MacDonald walked in."