You see Mad Sheep
"Maeh", "Groar!", "Fchhhh!".
Notes
This creature can only be seen when they are summoned by using the April Fools Day Spellwand.
Abilities
Self-Healing (looks like hearts), Strong Haste.
Damage Taken From Elements
Physical 
Death 
Holy
Ice
Fire
Energy
Earth
Location
Strategy
Just attack them, they don't do any damage.