You can get celebi, by getting the national pokedex and then ballte 100 unown, then celebi will copme up around level 15-25
The rarest Pokemon in Pokemon Diamond are the Pokemon you can not get in Pokemon Diamond, such as the Kanto, Johto, and Hoenn starter Pokemon (Bulbasaur, Cyndaquil, Mudkip, etc.), legionaries [Lugia, Ho-oh (Event Pokemon such as Deoxys aren't really rare), etc.], etc. Pokemon that are migrated from Pokemon GBA games are also rare Pokemon in Pokemon Diamond. Hope this helped! -Pyrenix three words mewtwo and mew The true hardest Pokemon to catch are: Deoxys, Mew, Celebi, Jirachi, darkrai, shaymin, Ho-oh and lugia that is because they are event Pokemon and the events are over, so to get them you need cheats, or trade them with someone who has, and they may not give them up easily.
No, you do not need cheats to get the rarest Pokemon. The only way to get the rarest Pokemon without cheating is to go to a Nintendo Event, held every few years or so, and download the rarest Pokemon there. Otherwise, you would need cheats to get the rarest Pokemon.
where are special key in Pokemon diamond where are special key in Pokemon diamond
Pokemon event.
well of course arceus but u can only get it on a wifi event
Wat
Arceus is a event Pokemon so get it from a event thing.
using a Pokemon event
Hackz or go to a Pokemon event
Dialga
arceus or shiny pichu event
Spiky-Eared Pikachu, in my opinion. You need to have a pikachu from an event to unlock it