Klein Bottle
aa = 3; ParametricPlot3D[ {(aa + Cos[v/2]*Sin[u] - Sin[v/2]*Sin[2*u])* Cos[v], (aa + Cos[v/2]*Sin[u] - Sin[v/2]*Sin[2*u])*Sin[v], Sin[v/2]*Sin[u] + Cos[v/2]*Sin[2*u]}, {u, 0, 2*Pi}, {v, 0, 2 Pi}, Boxed -> False, Axes -> False, BoundaryStyle -> {Thin, Black}]