Porygon's a great mon that works as others have mentioned as a great utility check to several of the metagame's most dangerous threats, including misdreavus, chinchou, and murkrow. Porygon fits bulky offense very nicely as it has a great list of options on how it can support its team other than checking a lot of threats like going offensive with a choice scarf or spreading paralysis. A really solid mon in my view.
I'll be giving it a run under the alt: Duck time
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