Sick jokes

I'd like to take this opportunity to thank my parents for all the days they stayed home from work and took care of me when I was sick.
I was in that position recently and now I realize how hard it is. Not the sitting around part: Waiting hand and foot on a pre-schooler who demands hot chocolate and endless reruns of Cars.
Nope, the hard part is the moral dilemma between work/school obligations and parenting responsibilities. In the end it took a wife willing to reschedule her morning, me getting permission to cut class and a son who can now quote Lightening McQueen line for line.
The cool thing is I was able to catch up on what's happening in Alex's life.
It seems knock-knock jokes have had as much impact on Barish preschool as the flu has. After about 40 knock-knock jokes, here's the best. Don't like them? Be thankful I didn't publish the other 37.

Knock Knock!
Who's there?
Tank!
Tank who?
You're welcome!

Knock Knock!
Who's there?
Boo.
Boo who?
Don't cry, Santa Claus will come next year!

Knock Knock!
Who's there?
Olive.
Olive who?
Olive you!

Want more? Try knock-knock-joke.com. One hundred pages of jokes, enough to make anyone stop answering the door.

Bonus joke:
Knock Knock!
Who's there?
Who.
Who who?
Is there an owl in here?