Easter egg
From MediaWiki

An Easter egg is a special treat hidden in something, (a comic book, a web site, a DVD) as a reward for the person who finds it. Since an Easter egg presumably requires extra effort to find or recognize, it represents a reward for the more 'hardcore' fan. The term has been in use for decades, while the practice of hiding information in artwork goes back millennium. Naturally, Transformers fiction (and occasionally toys) are replete with them.
Trivia
- Dreamwave was well known for including Easter eggs in their comics.
- Megatron Origin also features a large number of Easter eggs.
- The Universe ultra-class toy of Onslaught features a nod to uber-fan Monzo.
- The AllSpark Almanac is the undisputed king of the Easter egg.[1]

