I could be a zookeeper, but I'm not... - What you say when someone wastes your time with a stupid ide

What you say when someone wastes your time with a stupid idea that only they think is cool.

'I could be a zookeeper, but I'm not.' after my friend said he wants to be a unicorn trainer.

'I could be a zookeeper, but I'm not.' when my neighbor told me he wants to start a llama farm in his backyard.

'I could be a zookeeper, but I'm not.' after my mom said she wants to be a penguin whisperer.