Friday Night Lights star Adrianne Palicki will guest-star on Marvel's Agents of S.H.I.E.L.D. According to THR, she will play super spy Bobbi Morse, a.k.a. Mockingbird.
The character will appear in the fifth episode of the second season with the potential to return. The report says that "the episode will find her popping in perhaps not as an ally to Coulson (Clark Gregg) and his team."
The inclusion of Mockingbird was first teased at Comic-Con in July by Patton Oswalt, who plays Billy Koenig and Sam Koenig. He confirmed that Life Model Decoys exist in the S.H.I.E.L.D. universe, and also suggested that Morse's character could appear in season two.
Barbara Morse was a S.H.I.E.L.D. agent whose assignments made her an ally of the jungle lord Ka-Zar. She subsequently used the costumed identity of the Huntress and later Mockingbird to expose the corrupt activities of certain S.H.I.E.L.D agents. After being injured in her work she received a commendation by then S.H.I.E.L.D. Director Nick Fury, who used her information to expose dozens of subversives within S.H.I.E.L.D.
You can find some more information on the character at Marvel.com.