First you need to make a mental list of what pokemon the trainers had. Misty, Brock and Ash don't have half of all the pokemon that are cloned. Theres the pidegotto trainer, the Dewgong girl and the Water Gyrados trainer.
1. Watch the movie until mewtwo steals all the Pokemon from the trainers.
2. After Ash slides into the cloning room after Pikachu it shows Team Rocket in the cloning room watching the screen. They will say who's that Pokemon and then they say Alakazam! None of the other trainers had an Alakazm now did they.
If anybody can find any others that aren't shown just add a comment. I know this because every trainer can only carry 6 pokemon at a time and every one has 6 so how can there be a alakazam? Also when they all walk out of the ballroom to fight Mewtwo there's no Alakazam. There has to be an original if theres a clone.
Plus when theres the battle of the clones and the originals there aren't two alakazams