Popo is a mod that makes new things come out of IDPD and Van portals.  The further you get, the more chaotic everything becomes.

On a normal run you should see new IDPD spawns begin somewhere around Palace.

Not much more to it than that, and I don't want to really spoil anything, so I hope it adds some variety and fun to your game!

Also, a good thank to Blaac for IDPD Tank, sprites, and ideas!