WASHINGTON — Actor Seth Rogen botched his latest role, as the “celebrity champion for National Alzheimer’s Association,” when, in an enormous sense of entitlement — or perhaps just political naiveté — he razzed Sen. Mark Kirk, R-Ill., on Twitter for not sticking around a Senate hearing to hear his speech.

The fact is that Kirk had a very good reason for leaving the hearing after being there for most of the substantive part — where doctors who direct the national research institutes testified.

Celebrities show up all the time on Capitol Hill to promote their causes. The lawmakers like having stars testify because it shines a spotlight on their issues and maybe helps build public support.

On Wednesday, while Rogen testified about Alzheimer’s research before a Senate Appropriations panel, actor Ben Affleck spoke out about the violence in the Congo before the Senate Foreign Relations Committee.

Rogen clearly is passionate about Alzheimer’s. What he did not get is that in this town, jabbing a lawmaker who is with you — for the sake of a Twitter rush — makes it foolishly about you, not your issue. Kirk, a recovering stroke victim, met with Rogen privately before the hearing.

And posed for a picture with him. And then Kirk sent out on his Twitter the photo and the message, “thanks to @SethRogen for speaking out about efforts to #ENDALZ.

The Alzheimer’s hearing consisted of two panels — the first featured the directors of the National Institutes of Health, the National Institute on Aging and the National Institute for Neurological Disorders and Stroke.

Kirk was there for most of the docs’ testimony — he talked about the 10 Illinois pharmaceutical companies who want to bring to market drugs to find Alzheimer’s cures for patients.

After he left, Rogen said in a smarmy tweet: @SenatorKirk pleasure meeting you. Why did you leave before my speech? Just curious.”

Kirk left the hearing because he had a meeting with the president and CEO of Chicago’s Adler Planetarium, Michelle Larson, and retired astronaut Jim Lovell, who is featured in Adler’s “Shoot for the Moon” exhibit.

“Senator Kirk has long been a champion of the cutting edge research done at NIH, much like his predecessor in the House, Rep. John Porter,” Kirk press secretary Danielle Varallo told me.

As for the Twitter war that Rogen sparked, Kirk put out a one-tweet reply: that he was meeting with Lovell, watched his testimony — and asked him to “Keep in touch.”

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