What does it mean „I am smart just like that.”
I feel a bit of sarcasm but can’t get it…

Question

What does it mean „I am smart just like that.” 
I feel a bit of sarcasm but can’t get it…

Answer

I know the term "I am smart like that." (without "just").  It is usual a response to a comment.  John: "Wow!  How did you know how to fix the car?"  Mike: "I am smart like that." in that situation it means someone is intelligent in a certain or given situation.  You could also say "I am generous like that."  etc.  It is more arrogant if anything.

Answer

It is usually.....  In that situation.....

Please excuse the errors.

Answer

More context is needed