Building Portfolio by Pretend Clients and registering domains for them

Not sure where to post this so i am guess this is the right section of the forum for this any how,

i am trying to debate if i am wanting to build up some fake/pretend clients for my portfolio work should i go ahead and register domains for these fake clients? is this normal to do instead of using a subdomain for this kind of things im not sure if i should as i know i got a few ideas on my mind.

What are your thoughts on this?

No need to create all those domains. Just park them under your own in their own folders.

so add them as addon domain is what you mean??