#242 Blissey - Evolve from Chansey (level up after achieving high friendship)
#243 Raikou - Roaming Johto after initially encountering it in the Burned Tower
#244 Entei - Roaming Johto after initially encountering it in the Burned Tower
#245 Suicune - Static Encounter in the Tin Tower 1F after saving the director in the Radio Tower and receiving the Clear Bell and following Suicune across Johto
Note: After releasing from the Burned Tower, follow to outside National Park on Route 36, then the middle entrance of Mt. Mortar, then next to the Poke Seer\'s house in Cianwood
#246 Larvitar - Silver Cave Entrance, Inside, and Deepest (morning/day)
#247 Pupitar - Evolve from Larvitar (level 30); Silver Cave Deepest (morning/day) - very rare encounter
#248 Tyranitar - Evolve from Pupitar (level 55)
#249 Lugia - Static Encounter in Whirl Islands B2F after obtaining the Silver Wing from the old man in eastern Pewter City
#250 Ho-Oh - Static Encounter in the Tin Tower 10F after obtaining the Rainbow Wing. Requires catching/defeating Raikou, Entei, and Suicune on the current game cartridge (cannot be traded) then talking to a Monk in the Tin Tower.
#251 Celebi - Not currently obtainable on a Gameboy Color Cartridge through standard gameplay. Required connection to the Pokemon Mobile Phone System in Japan. May be available through exploits which may corrupt the save file, see this website: bit.ly/CelebiEggGlitch
On the 3DS Virtual Console - After defeating the Elite Four, receive the GS Ball at the Goldenrod City Pokemon Center and give it to Kurt in Azalea Town. After 24 hours, return to Kurt then take the GS Ball to the shrine in Ilex Forest for a Static Encounter with Celebi. This Celebi can be transferred to Pokemon Bank/Home legitimately.