This line is weird. I'm not sure if it's meant to be read as 'Look up slowly' (easily?), or 'The yukkuri looks up!' (meant in the same way as 'idiot says what?' 'what?' 'exactly'. The second applies if these faces are actually referred to as Yukkuri in Japanese, like they seem to be in English, but if they aren't, then it's the first.
Basically, I might just be reading too much into it. That aside, way to take the initiative, Marisa.
I don't know about you, but 'look up easy' isn't proper English to me. Even 'look up easily' doesn't really work... While I do agree it would be nice to put that in to keep the joke reference, it doesn't make sense and would be confusing. The word 'yukkuri' on its own means slowly/carefully, hence my word choice.
I think in MUGEN, they're called "yukkuri" and the other one is called "shiteittene" and the characters were clearly made by Japaneses. But maybe it isn't enough to know if they actually call them like that.