OK, so Little Case and I have been working on our act:
What did Buzz Lightyear say when he saw a frog and a toad swimming together?
Two amphibians in a pond!
Well, he thinks it’s funny.
Bwahaha I wish you had posted this earlier so I could have told my kids. They would have loved it.
Last February, we had some of my Califamily visiting in Buffalo - my aunt, my cousin, and her three-and-a-half-year-old Topher. My older sister made the mistake of telling Topher that joke that goes:
Topher found this screamingly funny and immediately tried to apply it to all situations possible.
If the original punchline didn’t garner the appropriate response, Topher would continue adding to it with anything he saw. “Banana-boo who’s walking outside… and… eating snow… and… a birdie!”
Nice kid, I suppose. 
I was a real brat with that “banana” joke about twelve years ago. I don’t get the amphibians thing though, unless there’s nothing to get. In which case–I get it 
I’m 41 and when my 37 year old brother told these to a small one I about pissed myself.
Knock knock.
Who’s there?
Impatient cow.
Impatie-
MOOOO!
Knock knock.
Who’s there?
Interrupting chicken.
Interrupting chi-
BAWK!
They’re killin me over here!
Nono, it’s a real punch line. The trick is to say in your most BOOMING BUZZ LIGHTYEAR VOICE.
As in, TWO AMPHIBIANS IN A POND!!
If you’re still not getting it, throw in a little pause after the word “amphibians”.
It sounds like Topher has confused the banana knock-knock with the “Boo who?” knock-knock. It also sounds like perfect three year old humor. When my son was a little older than that he mixed up the chicken crossing the road joke with the variation about the turtle. (Why did the turtle cross the road? To get to the Shell station.) We heard nearly endless repetitions of, " Why did the chicken cross the road? To get to the gas station."
He thought it was the funniest thing he’d ever heard.
Thanks for the spoiler box.
“Two amphibians in a pond” sounds like Buzz’s catchphrase, “To infinity… and beyond!”
No wait, come back, we have more material:
What do you call a baby ocelot?
An ocelittle.
He has this weird fascination with ocelots and walruses: I think he just likes the sound of the words.
I shaved my beard on Sunday. Now my 3 year old thinks that I’m the funniest thing she’s ever seen.
Also, burping is very funny. Apparently she’s become the class clown because she can burp on command and all the kids think that’s a hoot. I don’t know where she got it as neither her mother nor I make a big deal out of it. At least she says “excuse me” after every one (about 300 times a day).
Three year olds are weird.
I heard this one from a small kid about 6 years ago and I still laugh every time I am reminded of it.
Why do gorillas have big nostrils?
Because they have big fingers!
I know its infantile, I may grow old but I refuse to grow up