Stephen Colbert has praised unions on national television, walked a Writers Guild picket line and helped raise money for his staff during the Hollywood strike. Then he went to Harvard, where striking graduate workers had a question of their own: Would he honor their picket line?

Colbert and cellist Yo-Yo Ma went ahead with their talk Thursday night. Hundreds of protesters gathered outside, chanting loudly enough that people inside had trouble hearing, according to Cambridge Day. About 40 minutes in, during the question-and-answer session, a fire alarm sounded. Colbert was ushered out, and the event was called off.

Harvard and the fire department found no reason for the alarm to have gone off. The union denied involvement and said it didn’t know what triggered it. The chanting was theirs. The alarm is a separate question.

The graduate student union had asked both men to cancel beforehand. Ma is a Harvard graduate. Colbert had publicly backed striking Hollywood writers and helped launch Strike Force Five, a podcast that raised money for late-night staff during the strike. The union reminded him of that history and invited him to join its picket line. Instead, he went inside and took questions from a different audience.

Author John Green made the opposite call. He moved his Harvard appearance to Zoom to avoid crossing the line and donated what he made from the event to the union, The Boston Globe reported. So Harvard managed to get two very different answers from its celebrity guests on the same labor dispute. Only one of them came with a fire alarm.

The strike began Oct. 27. The union, which represents roughly 4,000 workers, says it wants better pay, independent procedures for harassment and discrimination complaints, and protections for international workers. Union spokeswoman Rochelle Sun said Harvard brought no proposals to the 36th bargaining session, held hours before the event. Harvard officials say they remain committed to a deal and have offered pay increases. Neither Colbert nor Ma had publicly addressed the incident as of the original reporting.

The funniest part is that nobody had to dig up some obscure old clip to make the point. Colbert had already made the case for respecting a picket line. The Harvard strikers just wanted him to apply it to the one outside his own show.