How to introduce Scala to a team of Java developers without being boring?
I'd start with something useful that takes yards of code in Java and only a few lines in Scala (assuming there are such things).

After two or three examples like this, you'll have hooked your audience. Move into a compare/contrast of language features. Talk about what's easier in Scala. For fairness, talk about what's easier in Java. Then move to how/whether you might adopt Scala in your workplace - or why it wouldn't be practical now but under what circumstances it might be.