This is a exploit of the compression algorithms to make a small zip that will extract into extream amounts their are more ways and better ones than this one but i will only show how to make a simple 1k = 1m ratio.
Followings are the steps
1) Make a.txt file
2) Open and type the null character (alt + 255)
3) Press ctrl + a then ctrl + v a couple times to make some null bytes
4) If u have a hexeditor make the hex 00 for about 50 kilobytes.
5) Now make several copies of a.txt and name accordinly
6) Open cmd.exe
7) Type copy /b *.txt b.txt
8) Now every copy is made into a super copy and repeat
9) Once you have a nice empty big text file like 1gb. Put it in a zip archive.
Because of the simple construction of the file, 1gb of null bytes.....!
The zip is only 1 mb in size and can really annoy freinds.
For added fun hex edit the zip and you will see a bunch of hex 5555
Just add some more and the file will expand amazingly
Make sure to not open this after
You can always create your zip of death from the command line in linux
dd if=/dev/zero bs=1000 count=1000000 | gzip > test.gz