First Monster

May I humbly suggest that "PacMan" should the first monster :)
Or as an inside joke, Dormant Doormats laying at the entrance to every doorway.
Wasn't there a DnD monster that did that?
Like a mimic, maybe?

http://www.dandwiki.com/wiki/SRD:Mimic

- Casey
Hehe Disguised Dormant Doormat :)