>>280734615
VIZ may have mucked up the last page, but they did spruce up Rokumon's line here, making a variation of the phrase "When the cat's away, the mice will play". Anyway, the original line was "思いっきり羽のばしてたじゃないですか。" which appears to not be a pun or even a set phrase and just translates to "You were really stretching your wings." But I can't be certain.