Put a hot carrot in the fleshlight

Putting a hot carrot in a fleshlight is a common method for prepping it just prior to use in order to more closely mimic the environment of a vagina.
If someone is to put a hot carrot in your fleshlight for you and you are not present, it would imply that they are expecting you promptly.
The phrase is used to notify someone that you will be present in the very near future. It has also evolved slightly through regular use to also mean that an event will be starting soon.