YOU SAID:

I watched an owl take a dump inside a train going towards a random cactus

INTO JAPANESE

私はフクロウがランダムなサボテンに向かって行く列車の中でダンプを取るのを見ました

BACK INTO ENGLISH

I saw an owl take a dump on a train going towards a random cactus

INTO JAPANESE

私はフクロウがランダムなサボテンに向かって行く列車でダンプを取るのを見た

BACK INTO ENGLISH

I saw an owl take a dump on a train going towards a random cactus