PD Ultraman Battle 64 is a Japan-exclusive N64 game that makes use of the Transfer Pak.
By connecting any GB cartridge, players can unlock a monster similar to the CD swapping feature in Monster Rancher on the PSOne.
Unfortunately, after trying many GB carts, I was only able to generate the same green slug and yellow Ultraman variants.
If you have used the TP feature in Ultraman 64 and spawned different monsters, leave a note in the comments with the GB cart you used so we as a community can potentially put together a list.
