2021 in Review: The Stealthiest Castings and Very Coolest Cameos

As much as we at TVLine aim to keep you apprised of fun and exciting casting news, the fact is that sometimes (though rarely!) TV shows enter super-stealth mode in the name of springing a surprise on all of us.

In fact, with Disney+ launching its slate of live-action Marvel series this year, 2021 packed a bigger “surprise casting!” punch than ever, using the small screen to introduce at least two new players to the MCU (while also making X-Men fans do a very fun double take).

With such casting coups and similarly delightful cameos in good supply this year, TVLine’s 2021 in Review has rounded up nearly 20 on-screen appearances that caught the audience at large off guard and/or teased us all with a fun wink-wink.

From Gordon Sumner’s involvement in a Murders plot to the Supergirl series finale’s crowd-pleasing encore, let’s revisit some of the year’s very best cameos and most secret castings — and then chime in with the ones you enjoyed most!