I was playing as Irelia against a Garen, I would make sure to tank a bit of the damage to ensure the stun would go off. Then as i would get my "e" off, it would display the stun animation over his character but he would keep on spinning and i would keep on receiving damage... Is this a glitch or intentional?
Stuns have never stopped abilities that already have been cast. Why on earth would you **ever **think it was a bug?
it isnt a bug. garen has always continued spinning regardless of the cc you throw at him. its part of his kit, why i have no idea.
Same thing with 
ult
It isn't a bug
It's a channeled ability like Fid's and Wu's ult, once started can't be stopped (except with a bard ult)
Check the wiki:
Judgment is not a channeled ability. As such, crowd control will not stop its effects. Silences will, however, prevent Garen from deactivating the ability early.
It's a PBAoE ability, but it isn't channeled so CC doesn't interrupt it.
Legends say Garen still spinning forever, until a knock up comes.
