The only way to "make" a mermaid is to download the appropriate outfit items and have your Sim wear them. You can not turn your Sims into mermaids.
You can't turn into a mermaid in any of the Sims games.
There is no such thing as a mermaid potion.
You can't, there are no mermaids in any of the Sims games.
I don't think you can.
You can't, sorry
You need apartment life to become a witch.
No, Double Deluxe is Sims 2 + Sims 2 Nightlife + Sims 2 Celebration Stuff
the sims 2 double deluxe is the sims 2 + the sims 2 nightlife + the sims 2 celebration stuff pack
Sims 2 double deluxe? yes sims 2 children grow up.
Uninstall the Sims 2 you already have and then install Double Deluxe
There are 2 discs in Sims 2 Double Deluxe. 1 for the game itself, the other for extra tips and tricks. ((the sims TWO double deluxe? I only have one..)
In the Sims 3 Island Paradise your sims can become a mermaid. In order to become a mermaid, a mermaid must give you the mermaid kelp or in life time rewards you can purchase it. Your sim must be human to become a mermaid (not a vampire, wolf, etc.)