'Stranger Things' Kids Get Down at Netflix SAG Awards After-Party |

LEAN BACK!

The kids from "Stranger Things" got in each other's face ... for an awesome dance-off!!!

The kiddos were getting down Sunday night at the Sunset Tower Hotel for the Netflix SAG Awards after-party ... and leading the way were Millie Bobby Brown and Gaten Matarazzo as Fat Joe's "Lean Back" blared from the speakers.

Actors Lonnie Chavis ("This is Us") and Marsai Martin ("Black-ish") also joined in on the fun. The kids went wild when Cardi B's "Bodak Yellow" came on. Huge little fans for sure.