Bangai-O
Enter "3 Groundhogs"
(found towards the end of the name entry list
of characters) as a name to unlock an extra
menu at the options screen and 44 levels.
The extra options are:
Riki's shot trail thickness: Normal (thin)/Thick
Mami's shot trails: Normal (thin)/Thick/Large
Missile/Thick (Nintendo 64 style)
Explosion Fragments: Normal/None/Heavy
Background: Normal/None/?
Invincibility: On/Off