Creeper don't respond to cats for a 5 second (about) period
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He means that creepers dont react to the cats, as they should run away when they see them. But I think this is not a bug, but a feature: The creepers dont directly notice the cat and only when they do, they run away.
I tested that, creeper always ran away when he got close to a cat, so unable to reproduce.

Another possibility for the delay could be that it is already processing another AI task, one that is not allowed to run simultaneously with the cat-avoidance task. For creepers, at least tasks "avoid cat", "wander" and "nearest attackable player" are mutually exclusive. I didn't check all of the creeper's possible tasks, but those three should already give an idea of how simple minded the creepers are.
Edit: oops, seems the 3rd task is on own set, the two firsts tasks in another. But still, there is at least that "wander" task possibly blocking/delaying the cat-stuff.
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Yeah I've found that eventually the creeper always sees the cat. At a certain distance though, it doesn't run away so much as, see the cat, walk somewhere else, wander towards me again, see the cat, run away. If the cat wanders too far away, the creeper can get close to me even with the cat present.
Seems to be working as intended to me.

Azure Klein: Indeed. The entity avoidance routine has two speeds to flee, depending on how close the frightening entity is. Also, once a creeper has finished its run, it is typically far enough to not see the cat, and may move closer again, even almost next to the cat (due to the delays) before noticing it again.
Whether that was the intended behavior or not is unknown, but the related code does not seem to have bugs/mistakes (only somewhat flawed or lacking overall design).
Can you explain in more detail what you mean by "not respond to cats"?