transformers
Mini-Cassettes are Transformers from the Generation One continuity family.
The cassette tape: the future of data storage and communications!

The cassette tape: the future of data storage and communications!

Mini-Cassettes (also known as Cassette Warriors or simply Cassettes) are Transformers whose alternate mode is an audio cassette. They can fit into the chest compartments of Blaster or Soundwave (while the toys can fit into either, in fiction they stick to the communicator of their own faction).

Many of the characters have communication or espionage roles. Also, many of them are redecos.

In the days of Megatron, Decepticons developed the art of espionage using cassette technology.
~ Teletraan II, from the Secret Files of Teletraan II
Japanese name: Cassettebot (Autobots) / Cassettron (Decepticons)

Fiction

Cartoon continuity

The Transformers cartoon

The Mini-Cassettes were largely subordinate to Soundwave and Blaster, and very loyal to them. They spent much of their time stored away in their chest waiting to be called out when the situation required it. The mini-cassettes with beast forms were treated like pets and were generally (but not always) limited to growling animal vocalizations.

Marvel Comics continuity

Generation One

Mini-cassettes were more autonomous and filled in regular positions in the ranks of the Autobot and Decepticons. They could all speak, but sometimes go long periods without talking.

Autobot cassettes

Main article: Autobot Mini-Cassette

Decepticon cassettes

Notes

Soundwave and his Mini-Cassettes

Soundwave and his Mini-Cassettes