Okay I got a couple knock knock jokes…
Knock knock!
Who’s there?
Horsep
Horsep who?
Haha you said horse poo!
Okay I got another one, you start…
Knock knock
Who’s there?
(Leave the other person hanging realizing they don’t have a knock knock joke handy.)
What’s the biggest city in the world?
Dublin. Because it keeps on Dublin, and Dublin, and Dublin…
This one is a bit dirty, so I’m hiding it behind spoiler blur.
A man’s sitting in a bar and he sees a gorgeous woman, drinking alone, looking sad. He walks over and says “What’s a gorgeous lady like you got to be sad about?”
“My boyfriend just dumped me because he thinks I’m too kinky,” she replies.
The man is stunned. “Wow. You’re not going to believe this, but my girlfriend just dumped me for the same reason.”
Well, the two talked and one thing lead to another and then went back to her place. They had a few more drinks, made out a bit before she stopped.
“Get comfortable,” she said. “I’m going to change.”
When she returned, she was decked to the nines in full dominatrix gear. Vinyl thigh-boots with six-inch heels. Fishnet stockings. Black leather thong. Riding crop in one hand. Bullwhip in the other. And as she steps out she sees the guy putting his coat on and getting ready to leave.
“Where are you going?! I thought we were going to get kinky together!” she said.
“Baby, I already took a dump in your purse and shagged your dog. I’m spent!” he replied.
Why do seagulls fly by the sea?
’Cause if they flew by the bay they’d be bagels! (Bay-gulls)
arrrggghhhhhhhhhhh 
Your mama’s so fat, Thanos had to snap twice.
(I like that one.)
If you see Bigfoot more often than you see your dentist, you might be a redneck.
(I wrote that myself… I’m selling if you’re interested, Jeff.)
A proton walks into a bar and orders a drink. The bartender asks, “Are you sure?” The proton says, “I’m positive!”
A neutron walks into a bar and orders a drink. Then, he asks how much he owes. The bartender says, “For you? No charge.”
I don’t have a good joke about electrons. I guess they’re just too negative.
This has been my dad’s favorite knock knock joke for decades! He always manages to make the interrupting cow extremely obnoxious 
That one writes itself. You just have to change the politicians name every 4-8 years.
I try not to make jokes about elections. Politics are too depressing to be funny.
Electrons, though. Those are a hoot! 
Would you say you get a charge out of them?
Indeed. 
When I was in the navy based in Charleston SC (1988-92), I used to listen to a morning DJ who would have children call in to say the pledge of allegiance and this one little girl called in to tell this joke…
She asked “What’s the difference between broccoli and boogers?
Children don’t eat broccoli!”
And now, my Doctor Who joke.
Ahem
Why is David Tennant afraid of Paul McGann? Because McGann Hurt Eccleston!
Whoa… that’s a deep cut, right there. 
Q: How many lawyers does it take to roof a house?
A: It depends on how thin you slice them!
When I was a kid, I was big on elephant jokes, such as:
Q: Why are elephants large, gray and wrinkled?
A: Because if they were small white and round, they’d be aspirin
Q: What’s grey and white on the inside and red and white on the outside?
A: Campbell’s Cream of Elephant soup
Q: What’s gray on the inside and clear on the outside?
A: An elephant in a baggie
I heard about this one in a different forum. You will either love this or hate it. Personally, I love it. It is a VERY LONG and strange tale before you get to the punchline. You’ve been warned. Read here:
https://natethesnake.com/
I’m having a crisis! 
I went looking for an MST3K Lightbulb Joke, and [sob!] nothing turned up! I was forced to clumsily cobble one together on my own.
Q. How many MSTies does it take to change a light bulb?
A. Two (Where Applicable)
Of course, there’s also riffs about eating light bulbs, being afraid of them, etc. So I’ll accept any and all better submissions. Thanks!
slight edit for your consideration:
A. Two. One to change the light bulb and one to turn it down (where applicable)
joke writing is not my forte 
That’s already an improvement. 
If we keep workshopping, it should be ready in time for the next convention or live show.