MySQL IN() statements: Avoiding duplicate lists
You can create a temp table, insert your parameters there and then join it:

create temporary table tmp (x int);
insert into tmp(x) values (10027),(11535);
select x.* 
from activities as x 
join tmp as y 
    on y.x = x.actor_id
join tmp as z
    on z.x = x.original_actor_id;