Time Capsule. You need to reach the Ecruteak City Pokemon Center on GSC and wait a day before you can trade. That is how I got my Totodile onto my Brown save file. For 2 reasons:
1. It got the EXP boost due to different OT and ID#.
2. Didn't want to waste time getting one from the casino.
Also, the Tri type (used only by Tri Attack on Brown) is a combination of the Ice, Fire, and Electric type. Take the weaknesses and resistances of those three types and meld them together. Example: Tri is good against Flying (Electric/Ice weakness) and completely useless against ground types (Electrical immunity). Thought I'd throw that out there also.
Now my question, what pokemon need to be traded to Brown for Pokedex completion? I want to *try* to get the prize, but I doubt I will get it. I only have about 70 pokemon captured on my pokedex.
And the prize, is it a pokemon or an item? Curiosity killed the cat ya know.