This is second hand, but I've been told by coworkers who tried to fly on an earlier Easyjet flight, that it's only possible if you are not checking bags (which can be difficult, given EasyJet's miserly carry on allowances).

Apparently these two tried to fly standby, but were told they couldn't because easyjet couldn't guarantee they could get the bags on the same flight if they were cleared at the last minute. And the bags had to go with the passengers. YMMV...