I've had my rat Mr Peepee for over a year now and two months ago I decided to get him a buddy (Milkshake). The reason why I waited so long to get him a friend was because the only pet store near my house didn't have a new shipment of rats yet, so I had to wait. At first when I introduced them, Mr Peepee would puff up and beat Milkshake up a bit when I put them in the same cage. I would always here frantic squeaking, but never any signs of a serious fight. They would act very calm and affectionate on neutral territory (once in a while Mr Peepee would bully Milkshake over dominance), but once They went in each other's cages they'd fight. Milkshake lives in a very small traveling cage and Mr Peepee, being a spoiled brat, lives in a 4 story cage that he doesn't like sharing. I noticed a few days ago they weren't fighting as much and when I put milkshake near Mr Peepee's cage, Mr Peepee didn't attack. A few hours ago (around 10 AM) I decided to put them both in the big cage together. At first Mr Peepee had a big hissy fight about this and wouldn't eat any treats I gave him, but after about 5 minutes they both calmed down and ate together. It's 4:30 PM now and they are both sleeping together in their hammock. They seem to be alright to live together, but I'm still afraid they might fight. I understand that boys will always be little bullies to each other, but I'm just worried because my previous rat, TG, killed his brother Junior in a fight when i was in school. I hate to see my boys be so lonely at night with no one to cuddle with, but I really don't want to have this happen again so I'm asking you guys for help to see if they can start living in the same cage.