Mr. Sunshine was peculiar, anyone who knew him would agree to that. But then again, anyone who lived with Brittany since they were a baby was destined to be a little peculiar. He did the typical things that all the other cats did: he napped, caught mice, and licked himself in inappropriate places in front of dinner guests. He played with string and feathers, he pounced on Brittany in her sleep when he wanted to play or go outside or if his food dish was empty. But there was something else about Mr. Sunshine that no one could really put their finger on.
Santana always made sure Brittany's bedroom door was shut when she spent the night, not only because more than once Mr. Sunshine had pounced on top of her when she was on top of Brittany, but because Santana had very strange dreams when the cat was curled up at the foot of the bed with them. She could never remember the dreams but every time she woke from one Mr. Sunshine would be staring at her. It honestly creeped her out. But somehow, that cat would always manage to find its way into the bedroom. Santana would just growl and cling to Brittany.
Quinn wouldn't let Mr. Sunshine in the basement with them when she came over to watch movies because he just sat there and stared at her. It made her nervous which made her heart race which made the baby move even more than usual. She was fairly certain that the cat was possessed, there was no other way he could make her feel that nervous just by looking at her. Quinn wasn't sure how he did it but that orange ball of fluff always ended up in the basement with them anyways and when she'd complain about it, Brittany would just smile and put her hands on Quinn's stomach and smile at the fluttering and kicks coming from within.
Rachel despised Mr. Sunshine. She had come over to give Brittany her homework when the blonde was out sick and Mr. Sunshine leapt out from behind the couch and onto Rachel's shoulder. The brunette shrieked and got a face full of cat before he jumped down and spun around in circles a few times before prancing off to the kitchen. Within minutes, Rachel couldn't speak because of the allergic reaction. All of the glee girls were a little relieved because Rachel couldn't talk about Jesse anymore and by the time she had her voice back they had split up.
Brittany loved Mr. Sunshine. It was weird when he started reading her diary, sure, but she loved him for it. She first thought he might be reading it when she was fourteen and things between her and Santana were shifting. She wrote that she liked it when Santana snuggled with her and shortly thereafter was when Santana started complaining about Mr. Sunshine causing weird dreams. Two years later, Brittany wrote in her diary that she liked feeling of Quinn's baby's kicks. Two days later, Quinn started complaining about the baby kicking too much when Mr. Sunshine was in the room. The final, definite clue that Mr. Sunshine was reading her diary was when Brittany wrote and complained about Rachel talking about Jesse too much. The next day was when Rachel brought her homework to her.
Mr. Sunshine adored Brittany. She had taken him in when he was a kitten and always played with him and cuddled with him and he knew he was loved. As for whether or not he actually reads her diary? You'd have to ask Brittany's little sister since that's the only person he talks to.