New insights I can learn from the Groovy language

Question

I realize that, for a programmer coming from the Java world, Groovy contains a lot of new ideas and cool tricks.

My situation is different, as I am learning Groovy coming from a dynamic background, mainly Python and Javascript. When learning a new language, I find that it helps me if I know beforehand which features are more or less old acquaintances under a new syntax and which ones are really new, so that I can concentrate on the latter. So I would like to know which traits distinguish Groovy among the dynamic languages.

What are the ideas and insights that a programmer well-versed in dynamic languages should pay attention to when learning Groovy?