Did you catch the Invincible Easter Egg in Sunday's episode of The Walking Dead?
Invincible is one of TWD creator Robert Kirkman's other comic books that he created and writes which is a take on Superman (but much more violent).
The Invincible mini-mates can be seen on the shelf below from the episode.
In case you didn't know, prior to The Walking Dead, MTV developed an Invincible animated motion comic series.
For the record, Kirkman has included Easter Eggs in all his projects ranging from Science Dog appearing in TWD comics as well as a comic of Invincible being given to Carl by Michonne.