Wizoob

Wizoobs are ghost enemies that disappear, then reappear near Isaac and spit a cluster of spectral tears (similar to ) at him.

Red Ghost
Red Ghosts behave the same as Wizoobs, but fire a beam instead of spectral shots.

Trivia

 * Wizoobs may be a reference to Wizrobes from The Legend of Zelda due to their similar names, similar sound effects, and attack patterns.
 * They could be a reference to Boos from the Super Mario series as well, considering that they look and act like boos, as well as having "boo" spelled backward at the end of their name.