There are two main ways to get a werewolf in Sims 2 they are both fairly tedious but worth it if you really want that werewolf sim.
The regular way
The regular way is much harder. First make sure you have The Sims 2 Pets expansion pack installed, next you must wait for the leader of the pack to come, he’s the black dog with glowing yellow eyes, you have a better chance of him showing up if you have a few toddlers and a few infants, after he shows up you need to have your sim befriend him. After they reach best friend status wait he will attack your sim after some time he will attack your sim, your sim is now a werewolf and will shift every night. Now if you want other sims in you family to become a werewolf just have the sim that you just made into a werewolf attack another sim at night when they are in werewolf form there is a new option :make a werewolf: just have them do that and the next sim is now a werewolf and will shift every night.
The cheating way
Now you still have to wait for the leader of the pack and you still have to wait for the leader to attack your sim but it’s a little shorter because after he comes and your sim greets him what you will do is hit the ctrl, shift, c buttons in the cheat box type boolproptestingcheatsenabled true, shift click your sim and hit spawn the select tombstone of L&D and hit make me friendly to everyone here then do any interaction that will increase their relationship, now wait for the pack leader to attack your sim. Your sim is now a werewolf
I think there is one other way with boolprop on shift click your sim and look for make me a werewolf if it is not there you’ll have to do it one of the two ways I described above
I hope that I have helped you in your attempt to get a werewolf sim.