My pretender is a Sphynx, thus immobile and huge

I was palling to teleport it amongts a few heathen wandering here and there. But to my abysmal disapointment, when I tried to cast the spell, I had a 'the unit is too immobile to be teleported'.
My question is : what does 'too immobile' mean ???
And of course : how can I teleport a Sphynx, then ?