There has been some talk ever since it was discovered that Raph would have a pet turtle. It seems that reactions have ranged from "That is a horrible ide" to "It'll be nice to see Raph with a softer side." No one really knows what extent this aspect will play in Raph's character, but it seems like it probably will be like Klunk for Mike.
I like the idea of Raph having a pet. It is something that hasn't been done before and adds something to his character just with the idea. After all he is always shown as being the hot head, brash, and not thinking. When you throw in the twist of a pet, it changes the mix. Is the hot head aspect going to be a game face for his brothers and others, or is the pet an idea Splinter comes up with to get his angry son to calm down?
Some people have thought that it would be possible that we may see Spike, the pet, become the evil turtle Slash. Now this is an interesting idea but it doesn't seem like it is something that I can see happening. When it comes to this it just is ludicrous. I don't see Raph being negligent enough that his pet would turn on him.
Something I thought about is what if Spike isn't really a pet but a 5th turtle that was in the bowl. That Yoshi finds four covered in the ooze and one not. Taking all four back to his lair the four start changing but Spike does not. When the four see the other Raph steps up and wants to take care of his "little" brother.
Whatever way they go with this I'm sure it will be a fun ride. I don't expect that this will be a big aspect of the show, rather a small little detail that will make this version more rich for being part of it.