Step 1: Understand the statements.
From statement 1: "All cats are animals" — this means every cat is within the category of animals. This does not tell us anything about whether cats are playful.
From statement 2: "Some animals are playful" — this means at least a part of the animal group has the property of being playful. However, we do not know whether these playful animals are cats or other animals.
Step 2: Test Conclusion I ("Some playful creatures are cats").
We are not given any direct or indirect link between cats and playful animals. The "some animals are playful" statement could refer entirely to animals that are not cats. Therefore, Conclusion I does not necessarily follow.
Step 3: Test Conclusion II ("All cats are playful").
There is no statement or implied condition that all cats fall into the playful category. The second statement talks only about "some animals" and not "all cats." Therefore, Conclusion II also does not follow.
Step 4: Logical Result.
Since neither Conclusion I nor Conclusion II can be definitely inferred from the given statements, the correct choice is:
\[
{\text{Neither Conclusion I nor II follows.}}
\]