Hopefully it never happens but should you run into a situation where your pet rat develops certain unwanted or undesired behaviors. Your going to have to address those to make sure that you can change the behavior and turn your rat back to a more appropriate pet.
The most common one that people are fearful of is biting, now the majority of rats do not bite and it's an extremely uncommon type of behavior problem. But it does happen in some rats. In the majority of cases, a rat that is a biter is a rat that has been a biter from when it was very young. It wasn't handled, it wasn't socialized, it was allowed to be in a sense kind of wild or untamed as a young rat and now somebody is attempting to force that rat to be social, to be friendly, to want to be handled when it hasn't been socialized to do that.
In this particular case, and if a rat is a biter and will pinch if handled or disturbed. You need to remember a couple of things, one of those is not to surprise them. Two, not to reach in and just grab them but always to let them know that your there, let them see you, let them see your hands. The third thing is you want to avoid being bitten and it may require wearing a glove, it may require wrapping the rat with a washcloth or a hand towel to be able to pick them up and restrain them.
It's also important to know at the times they may bite, the majority of times that somebody that has a rat that maybe an unpredictable biter. It may be that they pinch for no particular reason and this becomes difficult because then it creates a sort of fearful type of environment with your rat.
Like I said the majority of rats that do bite, tend to be those that haven't been properly handled or socialized and they bite out of fear more than aggression. Time and patience, handling, desensitizing them, teaching them to learn that they don't need to bite by a positive reinforcement. Sometimes teaching them to not be fearful of hands by offering them treats or favorite foods may help. And that'll help sort of curve the behavior of biting and hopefully break the habit if you have a rat that has been a biter from the time they were young.
Another problem that rats sometimes have that is not necessarily considered behavioral but is somewhat undesired, is the natural ability or their natural sometimes desire to urinate when they're first picked up or held. And many people find that if you pick up a rat and hold them, they may just empty their bladder at that moment. It's very difficult to train them not to do it, basically the best thing to do is try to ensure that they eliminate before handling or pick them up and then put them right back down so that they have a chance to pee before they can do it on you.
In most other cases rats don't make a lot of noise, they don't tend to be noise problems, they don't tend to have a lot of real serious behavior problems that become undesirable as pets.