Have multiple food deliveries scheduled for staff events.
This works best if food deliveries are not generally a part of staff events. Order food from multiple vendors and stagger the deliveries by 15 minutes.
For additional fun, leave different names with the delivery people. When more than one person from the meeting will be called away, the possibility of different ways of dealing with this awkward experience blossom. Include yourself in the middle of the deliveries to throw off other staff members.
Most people may not mind when the first delivery arrives. Individuals in an office environment tend to gravitate toward free food, and thus will be excited by the prospect. The management may even feel obligated to pay for the food once it arrives. After the second and third delivery arrives, the fun moves forward. Petty cash is generally not set up for hundreds of dollars in food deliveries.
Order what looks like good food, but will disappoint the zombies that open it. For example, order pizza with sun dried tomatoes, anchovies and onion. If you prefer to attack with food, order items with high dairy concentrations. It will not only make it more appealing, but may wreak havoc all night.