Awesome, glad he has a rat friend!
As for the plush, I wouldn't allow a toy with a squeaker personally, simply because it is plastic. Most dog toys use cotton or polyester (which is basically fake cotton and is a cheaper alternative to cotton, if I'm not mistaken) as filling. Even with dogs, people pick up the filling fairly quick. Dogs eat their toys all the time, so be wary of your rats doing the same.
Be wary of getting something (whether it be toy, cage, or any item regardless) marketed towards animals. Companies have a nasty habit of labeling something safe for an animal and it really isn't. Baby toys are a great route to go, because there are heavy regulations on what can or can not be in baby items. They also tend to be cheaper.