During his career, Cerebus had many encounters with other comic heros.
You may find a few more crossovers in other books, like Posters.
The appearances are sorted in the following groups:
Guest starring in comics, or having guests in a Cerebus
episode.
Posters and prints that introduce characters from other series.
The crossdressing department, where we find the Aardvark
wearing masks that don't really belong to him...
