Does Cho'Gath gain stacks from ulting clones?

If Cho'Gath uses Feast on Shaco's clone, LeBlanc's Mirror Image, Mordekaiser's puppet, etc., will he gain stacks from killing them?

And what happens if you Feast on Yorick while he has his ultimate activated?

Short answer: Yes/Yorick will die, revive and Cho'gath will gain one stack.

Feast (Active): Devours a target nearby enemy unit dealing true damage. Feast always deals 1000 (+0.7 per ability power) true damage to minions and monsters. If the target is killed, Cho'Gath grows and gains extra health. This effect stacks up to 6 times and Cho'Gath loses half his stacks rounded up upon death. Cost: 100 mana Cooldown: 60 seconds Range: 100

Source

• The meaning of "the targer is killed" count as Clones, minions, neutral monsters and others.

When you feast a target affected by Yorick's ultimate, and KILL him, you will get stacks. He WILL revive after that for a short time. But you haved killed him.

• The only momment Cho'gath does not gain stacks are when he DOES NOT kill the target. Like when someone is with Zilean's ultimate or Guardian Angel.

It doesn't matter who or what he kills,as long as he gets a kill with feast he will get stack.So yes he will get a stack from killing any of those,as well from dragon,baron,etc.