This isn't anything that will greatly impact the game, but I thought I would share it.

The Spoken Words used to regenerate monsters have a theme for each breed. I haven't translated them all yet, but here are some examples -

Baku - 'Delicious Noodles' (Ramen, Spaghetti, Udon..)
Beaclon - Insects (kamamiri [dragonfly], etc)
Colorpandora - "Table Games" (Mahjong..)
Dukken - Birds (ahiru 'duck', niwatori 'chicken')
Dragon - Dinosaurs
Falco - Rivers (amazon, nile..)
Golem - Mountains (kilamunjaro, McKinley, everest)
Hare - Meats (sausage. steak, vienna, bacon)
Mocchi - Sticky rice cake styles (ohagi, etc..)
Mew - countries (italy france..)
Ogyo - Gems (crystal, sapphire,diamond)
Piroro - Tecmo games! (dead or alive, ninja gaiden, monster farm)
Pixie - Snack foods (gum, potato chips, cake)
Plant - colors (orange, pink)
Tiger - Dogs! (chihuahua, poodle)
Lesione - Dangerous Animals (lion, puma, piranha, werewolf)
Suezo - Japanese places
Xenon - can't tell..
Zan - Continents (africa, asia, N america..)

Pixie's really planning on letting herself go.

What about Henger, Joker and Phoenix?

Henger has 1 spoken password, but it's very long and I can't quite figure it out. It's not really a them if it's only 1 word..

Joker and phoenix have no spoken passwords. They each have only 3 entries. The pure is made by a drawing. The Modoki is made by screwing up the drawing. The special are made by MFA1 and MFA2 cartridges...

Ah, fair enough.

Henger: 'ancient weapon that resuscitates'

Well, how about that?

can you obtain specials (/??? breeds) using themes?

Yes. There are a few.