DD1 is also 4 and will also get upset and hurt by things people say to her. I think at this age they do get quite sensitive as they are starting to understand feelings more and also the power that you can weild against others with these feelings. They don't fully understand empathy either so they do say and do things that hurt others.

I have found that she is going through a "silly" phase where she will say things like "that person is a bumbum throw them in the bin" loudly so that the person hears. I think she does it to get a reaction. I just tell her it isn't nice and I don't like hearing her say those kids of things.

It does sound like the tiger growling could be a shyness thing. If he isn't comfortable approaching kids he doesn't know or doesn't know what to say to start playing with them maybe do some role playing with him to get him to practice saying hello and asking names.