There are two types of membership on Moshi Monsters. You have to be a free Basic Member or a paid Moshi Member to get moshlings. However, you will not be able to get all of the moshlings as a free Basic Member.
Yes, you must be a member to take your moshling for a walk on Moshi Monsters.
You can not become a moshling on Moshi Monsters. You can attract moshlings to your Moshling Garden and collect them in your Moshling Zoo (if you are a paid Moshi Member).
You have to be a paid Moshi Member to have access to the Moshling Zoo through the Moshling Zoo Door on Moshi Monsters.
You have to be either a free Basic Member or a paid Moshi Member of Moshi Monsters to get the moshling Dipsy.
You have to be a member to have your moshling follow you.
No, you do not have to be a (paid) member on Moshi Monsters to get Peppy the Stunt penguin.
If you are a member on Moshi Monsters, the latest moshling you have captured will be following you. I'm not sure why though!
There is no moshling on Moshi Monsters named Big Ben.
You can get Chop Chop on Moshi Monsters if you are a free Basic Member or a paid Moshi Member.
You can not take your Moshling for a walk unless you are a Moshi Member (paid).
You have to be a moshi member!
You can not delete moshlings on Moshi Monsters. If you are a free Basic Member, you can choose "Set It Free" when you get a new moshling, but the moshling that you set free goes to your Moshling Zoo in case you ever get a paid Moshi Monsters account. If you are a paid Moshi Member, moshlings go to your Moshling Zoo.