This may be a way:
drawSphereRadius = 1/8;
Graphics3D[{Inset[Plot[x^2, {x, -1, +1}], {0, 0, 0}, {0, 0}],
Sphere[{0, 0, 0}, drawSphereRadius],
Sphere[{1, 0, 0}, drawSphereRadius],
Sphere[{0, 1, 0}, drawSphereRadius]}, ViewPoint -> Above]
Otherwise
Show[ParametricPlot3D[{x, x^2, 0}, {x, -1, 1}],
Graphics3D[{Sphere[{0, 0, 0}, drawSphereRadius],
Sphere[{1, 0, 0}, drawSphereRadius],
Sphere[{0, 1, 0}, drawSphereRadius]}], PlotRange -> All]