There's a problem of getting 'over the fence' - to reach the speed of light you need infinite energy - in special relativity you have a 'gamma' factor which goes infinite when v=c .
And it gets weird from there, the energy amongst other quantities goes imaginary if v>c. Possibly such things could exists from the get-go and thus wouldnt have to cross the v=c barrier, the idea is called 'tachyons' but I blv. no evidence exists for them and its not clear if these should be detectable.