Darf ich vorstellen: meine Schwester.

English Translation

I’d like you to meet my sister.

This feels like an odd word order in German compared to “darf ich meine Schwester vorstellen”.

That’s because it’s secretly two sentences. The colon hints at this, and there is also a pause when speaking.
Darf ich vorstellen? (Das ist) meine Schwester.


As always a perfect explanation by pitti42.

I just want to add that whereas “Darf ich vorstellen:” needs no object, “Darf ich meine Schwester vorstellen” sounds a little bit odd. Better: "Darf ich Ihnen/Euch/Dir meine Schwester vorstellen?
“Darf ich vorstellen:” is usually used crosswise. “Meine Schwester.” and with a look to the other side e.g. “My new neighbours Anne and Tom.”