Here's why it fits your description:
* Little blue guys: The Smurfs are small, blue, and humanoid.
* Mean: While not always malicious, the Smurfs can be mischievous and sometimes even cause trouble.
* Turn good: The Smurfs are generally good-natured and often help each other and other creatures.
* Tape: This suggests a home video format, which was common for cartoons in the past.
* Dreamland: This might be a reference to the Smurfs' whimsical, magical world.
The Smurfs were a popular cartoon series that started in the 1980s and was widely distributed on home video. It's very likely you saw them on a VHS tape!