gy ▁get ▁ro ped ▁into ▁pil oting ▁the ▁dog ▁ro ver . ▁ ▁On ▁the ▁ro o ft op , ▁Sh ag gy ▁and ▁S co oby ▁find ▁Me cha ▁M utt . ▁After ▁a ▁fight ▁with ▁miss iles ▁and ▁ro cket ▁boost ers , ▁the ▁two ▁machines ▁crash ▁into ▁a ▁magnet - w ield ing ▁c rane ▁and ▁Me cha ▁M utt ▁is ▁destroyed . ▁Vel ma ▁ident ifies ▁Mel anie ▁as ▁the ▁cul prit ▁behind ▁Me cha ▁M utt ' s ▁r amp age . ▁Mel anie ▁adm its ▁that ▁she ▁did ▁it ▁because ▁her ▁famous ▁father ▁always ▁neglect ed ▁her ▁and ▁she ▁wanted ▁to ▁step ▁out ▁of ▁his ▁shadow ▁to ▁prove ▁she ▁was ▁just ▁as ▁brilliant ▁as ▁him . ▁In ▁the ▁end , ▁Fred ▁wins ▁second ▁place ▁in ▁the ▁Science ▁Ex po ▁and ▁Sh ag gy ▁and ▁S co oby ▁end ▁up ▁finding ▁more ▁than ▁just ▁astr onaut ▁food ▁when ▁they ▁end ▁up ▁accident ally ▁launched ▁into ▁outer ▁space . ▁ ▁Cast ▁ ▁Frank ▁Wel ker ▁as ▁S co oby - D oo , ▁Fred ▁Jones , ▁Pres enter ▁ ▁Matthew ▁L ill ard ▁as ▁Sh ag gy ▁Rog ers ▁ ▁Mind y ▁C ohn ▁as ▁Vel ma ▁D ink ley ▁ ▁Grey ▁Del is le ▁as ▁D aph ne ▁Bla ke , ▁L oud ▁Spe aker , ▁Re porter ▁# 2 ▁ ▁Jul ie ▁Bow en ▁as ▁Dr . ▁Dev on ▁Al br ight ▁ ▁Phil ▁La M arr ▁as ▁Stan , ▁Mission ▁Control ▁ ▁L ace y ▁Ch