Misprint, error, or just bad Pokemon card logic?

Question

So, I have a grass Koffing and a psychic Gulpin. Error, misprint, or bad card logic?

Answer 1

Prior to the Diamond/Pearl Gen IV sets, Poison type Pokemon were released under the Grass typing for the TCG. Starting with Diamond/Pearl, they moved over to the Psychic type. This was likely done so that cards under the Grass type were more uniform in having a Fire weakness, in order for them to balance out the colors a bit and provide a more coherent color identity.

Comments

so first of all, you downvote the first answer,
second, choose your own answer,
last of all, not even answer what i asked in the title.

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I downvoted the first answer, because it was in error. I did not choose my own answer, another moderator did, likely because my answer was correct. And it did indeed answer your question. The reason you have a Grass Koffing and a Psychic Gulpin is because of the change in type between sets for the Poison type Pokemon. It is neither an error, misprint, nor bad card logic. It was a decision to strengthen the identity of each type and make them more coherent.

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Oh. Ok. (12 characters)

Answer 2

Bad card logic. There are many cards like that. For example, I have a Larvitar Fighting type, Swellow Fire type, and Garbodor Psychic type. I believe the general rule for types that don't have an energy are Rock and Ground to Fighting, Flying to Electric or Normal, Poison to Psychic, Ghost to Dark, and Ice to Water.

Source: my own cards

Comments

And Bug to Grass. Forgot about that one.

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The fire type swellow is most likely a delta species card, where the pokemon were purposefully given a different, abnormal type. I have a psychic Typhlosion and a couple steel Pikachu, for example.