At first, Papyrus had seen nothing wrong with Gaster.

He made his brother happpy, the both of them exchanging puns, and sharing a lot ve of science.

They would hang out during their work hours, or anytime they could.

The first time Papyrus had suspected anything to do going on was when Gaster asked for one of their of Sans' sweaters.

"Sans asked for his sweater." Gaster had (cutoff)

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Papyrus could tell if there was romance in the air.

He figured out that Undyne had a crush, and could give romantic advice. Although most people thought it was bad advice, it was the best he could do.

He could also tell if someone was crushing on him. (However rare an occurance that was)

However, Sans was different. He was smart with anything else, other than romance. When they had been younger, quite a few people liked hum, but he never noticed.

These are really bad