isnt amumu supposed to not have any freinds?

he always was friends with annie

Any has been this weird exception to that rule since time immemorial.

Amumu has been friends with Annie since forever ago

Annie isn't a nice person, she is probably like an Angelica to him.

Him being friends with Annie might not be Canon anymore anyway,the official pages almost never update,thats all.(Yorick is still listed as one of Hecarims friends,even though Hecarim should be one of Yoricks worst enemies)

This was when Riot wanted all the champions to hold hands with one another. I loved how it was Friend/enemy there's no in between they either get icecream together on the weekend or they rip each others faces off. The lore is soooo good.

Chinese Splash tho [slayer-jinx-unamused]