A joke for lack of anything better to write

I read this joke in a book by Isaac Asimov recently.I would like to thank him for his contribution-albeit unbeknowenst to him-to this post.I hope Im not breaking any copyright laws.

It was during the war and Ole Johnson had come back on furlough to his little town in Minnesota.He was an air pilot and had done wonders,and the princpal of the local high school thought it might be very nice if Johnson would give a small talk to the students and recount his air adventures.
Johnson was perfectly willing to do so,and there he was on the stage of the auditorium,with red,white,and blue bunting everywhere,and with the eager faces of the high school students listening eagerly.
The talk went swimmingly as Johnson spoke of training and preparation,and finally of air battle.
He said,"At this time I managed to fly far behind enemy lines,but didnt know it.I thought I was safe and I was even singing a little Swedish folk song,when all of a sudden,out of the clouds,came two Fokkers.I snapped to attention and sent my plane climbing in a wide circle and,descending,I got one of the Fokkers in my sights and shot him down.I then turned to the other Fokker,who was closing fast,when I noticed that three other Fokkers were approaching from the other direction- "
With each repetition of the word Fokker there was increasing hilarity from the students,and it was clear that they were getting out of control.
The principal was equal to the occasion.He rose to his feet,held his arms high for silence,and said"Students,the Fokker is a German warplane that was first designed by an engineer named Anthony Fokker"And,turnung to the speaker,he said"Isnt that correct Mr Anderson?"
Anderson looked confused.He said,"Yah,you are right,Mr Principal,but these Fokkers I was fighting were Messerschmidts."