Pokemon that count as one of Ash's OS pokemon and those that evolved in the AG/DP era that don't count as Ash's OS Pokemon.

[Piii]

I know some people count Donphan and Quilava as Ash's old Johto Pokemon, but they don't count as Ash's old Johto Pokemon.

Phanpy evolved in a filler saga and Donphan was part of the BF team not the Johto team.

Cyndaquil evolved in Sinnoh and at the time it did happen it was done to tell it apart from Dawn's Cyndaquil that she had at the time, Quilava was part of the Sinnoh team and not the Johto team, because he was used along side with the Sinnoh team.

Feel free to voice your opinions