Sirius had resigned himself to getting punched in the face often. Not that he minded that Brainy had refrained. Even if this was all an elaborate hallucination he didn't imagine it would be too pleasant.

But he was blissfully unaware of how close his nose came to being broke. So instead he continued to grin.

"Oh Moony, what's the fun in warning them," he said flippantly before turning to Brainy. "Don't worry. You won't make yourself hoarse." He turned to the others, raising his wand. "This won't hurt a bit." As a show of good faith, he cast the spell first on himself before casting it on his companions, one at a time.