Poppy ULT doesnt stop Kogmaw
[zombie-brand-mindblown] I ulted Kog'maw and my ult was is, as you know, supposed to stop any damage or ability from one champion for 7 seconds (at the level my ult was at this point) but he kept hitting me.
BUGGY! 
[zombie-brand-mindblown] I ulted Kog'maw and my ult was is, as you know, supposed to stop any damage or ability from one champion for 7 seconds (at the level my ult was at this point) but he kept hitting me.
BUGGY! 
Nope. Your ult stops damage from all other champions than the one you ulted, but only for this patch. Read the tooltip.
[zombie-brand-facepalm]
The guy you ult is the one that can damage you. not the other way around...
Read the ability tooltip
It's the other way around: It's all damage EXCEPT the one you ult: Basically if Poppy ults you, it's your job alone to try to stop her from wrecking everything around her.
Or you know, just wait a week or two for her rework to go live.