If those pesky Achievements for the game are to be believed, Viva Piñata: Trouble in Paradise will support four player online co-op. 360sync.com lists all the "bleep bloops" for the upcoming candy-filled animal simulator and one 10-point achievement, named "Full House," comes with with the description: Play 4 Player Online Co-op for 1 hour.
We're still not exactly sure what co-op entails, as there also Achievements listed for playing two player co-op, both online and off, for one hour. We should get more details soon before VP: TiP starts getting whacked at retail on Sept. 2.