Professor Oak

Professor Oak - The friendly old man from your hometown in Red/Blue/Yellow.
I don't know if you can still remember, but whenever you tried to use an item in Gen. I + II (+ Fire Red/Leaf Green) you can't use at that time, e.g. the bike in a house, Prof. Oak would say something like: "(Player Name)! This isn't the time to use that!" He is watching you.

Pokémon Blue

Pokémon Crystal

Fire Red

In Gen. III and following generations he stopped doing that.

Pokémon Sapphire - "DAD always says...."

Pokémon Platinum - "Prof. Rowan always says..."

Pokémon Heartgold - "Prof. Oak always says..."

Pokémon White - "Prof. Juniper always says..."

Thanks to omega_metroid for the hint.

Pics are taken by me. And sorry for the messed up design.