To obtain this trophy you must obviously go to the Yucatan Casino, but before Snowflake and Ted are gone. I am not exactly sure when they disappear (but I'd recommend going there early on in day one).
*** Spoiler - click to reveal ***What you must do is kill Ted which isn't that difficult then either kill Snowflake, which can be a pain if you are a low level, or tame Snowflake (in one of two ways)
Way 1: get 3 steaks and lure Snowflake to them until he becomes friendly
Way 2: kill Ted then wait until the end of the day for Snowflake to become friendly (unsure if Lenny will vanish though...doubtful but I'll check).
Now after the boss is killed in the casino you want to go to the managers office and save Lenny. Then you will be able to turn on the power unlocking the trophy.