One of Lance's Dragonair 'locked into' Agility; a Psychic type move, against Zubat, a Poison/Flying type Pokémon.
In Pokémon Red, Blue and Yellow, enemy Pokémon from computer controlled Trainers (but not wild Pokémon) prioritize super effective moves over regularly effective or not very effective/non effective moves even if the move does not deal damage.
The AI was changed in Pokémon Gold and Silver so that opponents will not always use a non-damaging super effective moves if no super effective damaging move is known. (e.g. Bird Keeper Jose's level 34 Farfetch'd on Route 27 will not be locked on to Agility against a Zubat)
In Pokémon Red and Blue, all three of Lance's Dragonair know Agility as their only Psychic-type move. Agility is a status move rather than a damage dealing move, however, these Dragonair will be 'locked on' to Agility against a Poison type Pokémon such as Zubat, because the Psychic type is super effective against the Poison type.
A low level Poison type Pokémon could eventually beat one of Lance's Dragonair, and the process could be made quicker with a poison inducing move such as Toxic.
As enemy Trainers don't use PP in Generation I, Dragonair running out of PP on Agility is not a problem.
- A thread on the forums about the flaw.