Whether it was intentional or not, he chuckled at the pun the inkblot made before telling him:

“It does no longer matter, our train is gone.” While he was considering any other options to get where they wanted, he noticed the blob fixing the crack he unintentionally left.

“What’cha doin’? ” he had a slightly mocking tone, but he seemed genuinely curious too; like if he didn’t know what he really did.

“Oh,” the Repairman said, evenly. “Sorry to hear that.”

He looked back at what could loosely be described as his handiwork (it was a slapdash job, after all).

“Oh, this? This is–”

He stopped, realizing he was amongst toons. Mentioning the fourth wall so openly was not a smart move. He pulled out a piece of paper and carefully rolled it into what would (hopefully) be an effective silencer.

Putting it up to where Cuphead’s ear would be, he whispered “I’m fixing the Fourth Wall.”