With the launch of vSphere 6.0, the Instant Clone feature was released that allows you to do rapid in-memory cloning of running VMs. If you’re not aware of the feature, it has been known as VM Fork or Project Fargo (prior to the release of vSphere 6)….. Duncan Epping has a great write up on his blog: http://www.yellow-bricks.com/2014/10/07/project-fargo-aka-vmfork-what-is-it/
Unfortunately it was an API that was hidden away…. but the latest VMware Labs fling extends the functionality of PowerCLI to grant you access to the API.
Worth having a look…. but as always, only in a dev environment! =)