TweetCaster’s unique “Make It My Own” feature allows you to easily copy an existing list.
Tap Add A List and then tap “Find Existing List”. Enter the name or Twitter username of someone to search their lists. Once you find a list you want to copy, select “List Profile” from the menu then select “Make It My Own”. You can then rename and add a description to the list if you choose.
Click “Next” and you will be given the option to remove members from the list. You may also add people to it. Click Save to add it to your lists.