There are TWO WAYS they follow the RULES of the forms
Option 1: DNS SETTINGS
A really cool and interesting thing that was discovered was the use of DNS setting on the DS (which the 3ds still has) you basically set up your wifi in a way that it connects to a server or some funny thing to obtain LEGAL AND LEGIT POKEMON. This requires no HACKS and is not a GLITCH. It is just not intended.
There is a little more to it. Your wifi MAY NOT CONNECT TO THE DS PART. Your wifi will connect to the 3ds but the Wii and DS were are older and can't connect to some WIFIs. You may want to set up a custom access point with your wifi (if you are the owner then this would be easy) or use a mobile hotspot and change the GHzs on it. From my knowledge and experience, it will most likely work on the 2.5 GHz. IGNORE THIS IF THE DS CAN CONNECT TO YOUR WIFI WITH ZERO ISSUES
- You will then use a DNS setting to change what you will connect to. This basically with give you a specfifc event Pokemon or something like that. this is vague not because I am unsure it is because how it works sometimes may not work or not work as intended like it will give you the wrong Pokemon
You should search for DNS GEN 4 in order to really read or look at videos yourself.
Option 2: Void Glitch
This option is possible in Pearl and Diamond, but not Platinum. Ima be real with you. This is the hardest one in terms of time and precision. However, this has been CRACKED to the max by people (gamefreak thought we were too stupid to use a flute so we took that personally) all I can do is provide a link to a YouTube video that performs it PERFECTLY.
https://www.youtube.com/watch?v=JrWct9U9rhM
Other than that if you magically had the distribution cartridges then these are the only ways. BTW HGSS and BWBW2 have this DNS stuff too!