Christopher Ryan is indeed very small. He was chosen to play a Sontaran in Dr Who a couple of years ago because of his height.
Several years earlier in Doctor Who, Ryan played Lord Kiv, a Mentor (a sort of diminutive green humanoid seahorse). The more famous mentor was Sil, brilliantly played by the truly tiny Nabil Shaban.
what about Dudley Moore he is only a tiny 5′ 2½, He was frequently referred to in the media as "Cuddly Dudley" or "The Sex Thimble", a reference to his short stature and reputation as a "ladies' man". Then theres Micheal j Fox who is only 5′ 5.