Leo:
A lot like he is with April. He's a shoulder to lean on and he trys his best to give you advise when you need it. It will take a little for him to be comfortable enought to open up to you, but once he does, it's safe to say there will be weekly therapy sessions for the both of you. He can't really cook but I see him trying to make you cookies. Definitely a mom friend.
Raph:
Similar but not the same as he is with Casey. Depends of what your personality is like. Are you loud and funny? I see him cracking joke with you or telling you to shut up with a smile. Are you shy or quiet? He finds you a little boring but respects it. Are you athletic and cocky? Well he finds you annoying but he relates to you a lot. It will take...literally forever for him to actually open up and even then it's awkward.
Donnie:
Hes..well I see him trying to be a loyal and good friend to you. Depends on how you act around him. If you are too much like raph he'd probably avoid you. If you let him rant about tech without interrupting your trying to shut him up I see him glued to your side forever. Though I also see him catching feelings REALLY easily so watch out.
Mikey:
This guy could pack bond with a brick, he wants friends so badly. You don't really have a choice in the matter to be honest. But it you let him be 'loud' and 'annoying' around you without being mean or telling him to shut up he will be loyal to you forever. He wants to do anything and everything with and for you. Count on a lot of small gifts like shinny rocks or peices of broken jewelry he found.