Renaming

Try Grassle or MJle

But why are you naming a Pidgey Weedle?

That is strange. It will let you rename a weedle pidgey though

Interestingly enough, you can rename a Weedle to Weedle, but no other Pokemon can be called Weedle. I bet it has to do with the word "Weed". I'm guessing that Niantic has instituted some heavy filters on Pokémon names so that you're not trading Pokémon with "unacceptable names".

Other ones I've run across:
-Anything involving common words for Genitalia
-GSpot and Pot (but not Spot, so it's probably a fairly advanced filter)
-Any ethnic, sexual, racial, etc. slur
-Most obscenities
-Some nicknames for drugs (smack, pot, weed, etc.)