It looks like the current "feast" feat is going to fail to reach its goal, so here are some ideas for a do-over:
Have an in-game event that involves food. Perhaps the goal could include a combination of cooking, eating and donating food to shrines -- with each of these actions counting towards earning some kind of reward. Successful completion of the feat will unlock new content or features, but with the added twist that the exact nature of what's unlocked will depend on which giant gets the most donations of food during the feast.
Because there are in-game rewards for cooking, eating and donation, the rewards for participating in the feat can be modest. However, for this feat, let every participant get some kind of trinket that they can keep as an "I was there" souvenir. There can be one item that most players get, making it not very rare -- kind of like a "free beverage with meal" prize.
Concurrent with the in-game activities, ask players to invite friends to Glitch. But give a soulbound reward to the new players who accept the invitation (perhaps subject to a time limit) rather than to the players who give the invitation. This provide a rationale for inviting people now (vs. last month or next month) and makes them feel treated as an "end" rather than as a "means." If you want to also reward players for invitations, make that ongoing and mundane (i.e. credits, iMG) -- and perhaps limit it to invitations that are accepted rather than simply extended.
Hold the do-over feat during a weekend, but advertise it in advance so players have a chance to manage their schedules accordingly.