Neat vid. had some funny moments and nice action (like the parts where rainbowdash and sonic would have speed boosts). I would recommend that if you made another sonic vs rainbowdash vid or something similar to that, there should be more movement of stop motion. like the sequence where sonic is jumping between mountains seems somewhat static and when sonic curled into a ball, there should be more shading. and a slight nit pick is that rainbow dash didn't have the rainbow stream following from her very often as she flew, but that's just an aesthetic nitpick. the character interactions were humorous and some action sequences had a consistent pace (also it seems your drawing/model of sonic is in slightly better proportion (even head, pupils) just a small thing)