Again, another entry where the punchline of the joke is somewhat deflated by the heading, which effectively is the punchline. So, you ask "Have you ever had a big juicy fanny wrapped around your head?", and they say "No", so you say "Eurrrq! Test tube baby, test tube baby!"

Calling somebody a test tube baby is a great insult; because as well as suggesting that they haven't got a mum, it also proves that their dad likes going to the hospital and wanking into a dirty cup for 5p.
a: "Can you climb up glass?"
b: "No."
a: "Then how did you get out of your test tube? - Is your star sign 'Pyrex'?"

I was concieved via IVF; in fact I was one of the first 5,000 ever concieved in the world. So I got to go to Thorpe Park at age 6 and YOU didn't, you bunch of boringly-birthed old sods.
Hahaha. Your dad done a wank.

at my school we used 'Skip baby' in the same way to insult sum1 as to say they have no mum, but are WAY too fat to fit inside a test tube.

Other varietys included 'Crater baby' and 'Moon Baby'...didnt understand the Moon Baby one...but neither did they, so it was still funny

As a, ahem, 'portly' child, my only recourse was to fight fire with fire and mercilessly take the piss back out of everyone who may even dare comment on my size. A cheap shot this one, but nevertheless, an inspired jape: a kid in our class who was, I am sure, actually a perfectly nice young fellow, was not the most popular lad around and, being of French descent, was ripe for the piss-taking. Couple that with a name which was perfect for shouting across the classroom in a chin-poke-tastic mong-voice ("Ugh, Greeewweeeeey") and I couldn't resist the rather obvious gag in one Chemistry lesson. Smashing his test tube-based experiment on the floor, "Ugh, Greeewweeeeey, I just killed your mom!" I cried. "Fuck off you fat cunt" was his rather basic and lamentable retort as the class joined in mocking him ("Greeewweeeeey's mom's a test tube, Greeewweeeeey's mom's a test tube"). A detention for swearing and damaging school property was the outcome...for him...hahahaha!

Me: You must have really long arms.
Victim: Eh? Why?
Me: To have climbed right out of the "Abortions" bucket.