>I read once in "Quant" (?) (Russian magazine for Maths) sequential jokes (puzzles), e.g each answer should continue the previous one. E.g.
>
>1.How many steps do you need, to put a hippopotamus (?) into refrigirator?
>
> 3 steps:
> 1.Open regrigirator
> 2.Put a hippopotamus here
> 3.Close refrigirator

The famous "Teapot principle", which generally describes this approach used in physics and maths exercise books:

Problem: you have a stove, water, sugar, tea, teaspoon, electricity, and a teapot. Make tea.

Next problem: same as above, except that the water is already boiling in the teapot.

Solution: spill the water. That brings us to the previous problem we have already solved.

>2. How many steps do you need, to put a giraffe into refrigirator?

Four more:
1. open the fridge
2. get the hippopotamus out
3. put the giraffe in
4. close the fridge.

Q: how do you put four elephants in a VW beetle?
A: two front, two rear.
Q: how do you put four giraffes in a VW beetle?
A: nearly impossible unless you get the elephants out somehow.

>A boy jumps from 8th stair and breaks one leg. From which stair should he jump to break two legs?

No can do (or "will not can", best translation from the Serbian "neche mochi" I could manage)- he has only one leg to break now.