Responding to criticism from fans that there were not enough connections between the Marvel Universe and the Marvel’s Agents of S.H.I.E.L.D. TV series, Marvel has announced that, in addition to the already announced appearance by Jamie Alexander as the Asgardian warrior Sif (see "Sif to Appear in 'Agents of S.H.I.E.L.D.'") two more well-known Marvel characters will make their appearances in the second half of the show’s first season.

In fact one of them has been there since the first episode.  Marvel revealed that Mike Peterson (played by J. August Richards), a sympathetic character, a single father who was given special powers by Centipede, will become Deathlok, the cyborg created by Rich Buckler and Doug Moench who first appeared in Astonishing Tales #25 in August of 1974.  In all there have been four iterations of Deathlok in the comics with one common denominator--they all died and were reanimated with cybernetic technology.
At the end of the episode "A Magical Place" it was revealed in a post-credits scene (evidently Marvel has now made it imperative to sit through the credits of both their movies and TV shows) that the explosion at the end of "The Bridge" episode badly damaged Peterson, severing his leg and damaging his sight.  In the new episode "T.R.A.C.K.S.," which airs on February 4th, Peterson becomes Deathlok with an eye implant and a cybernetic leg.  The question is, will he fight with S.H.I.E.L.D. or against it?
Lorelei, who will be played by Elena Satine when she appears on S.H.I.E.L.D. in the same episode in which Jamie Alexander reprises her Thor movie roles as Sif, is a gorgeous red head who, thanks to her beauty and seductive powers, has the ability to persuade virtually any male god or mortal to do her bidding.  Lorelei, who is closely based on a character from German mythology, was created by Walt Simonson during his great run on Thor and made her first appearance in Thor #337.