If you cant remember, here is a list of all of them:
https://wow.gamepedia.com/Category:April_Fools
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For me:
1) Equipment Potency EquivalencE Number (aka EPEEN)
https://wow.gamepedia.com/Equipment_...valencE_Number
Funniest thing ive ever read.
2) P1mp My Mount!
https://wow.gamepedia.com/P1mp_My_Mount!
Holds a special place in my heart because it actually fooled someone in my guild...we all laughed.
3) Introducing the Tinfoil Hat
https://wow.gamepedia.com/Introducing_the_Tinfoil_Hat
Im actually diagnosed with paranoia IRL...so...this is kinda funny to me now that i dont have an episode in years (>_<)