To provide some context, Lion-Moose have a rivalry relationship in the series before they become friends at the end. Though Moose is still all about the competition while Lion just wants to chill. At the end of the last ep, Moose met another big cat - Jaguar and commented about how she looked strong and seemed to be interested in fighting her.
The parody here is the gaijin 4koma, the 3 in the 3rd panels are all very strong animals (jaguar, wolf, bear) and that's why Moose is interested in them (much to Lion's dismay).
I think what really sells this is how intimate it is. It's nothing hot and heavy, there's no overt sex or kissing or even hand-holding. But there's an ease entering into each others' personal space and performing a very personal act, and here's Kaban with a smile on her face and Serval totally caught up in what she's doing. I love stuff like this.