[panel 1]

The Other One: Wow, you actually uploaded that one?

The photo from the previous episode has been uploaded to Instagram.

[panel 2]

The Mother: Yup! Look, this one's even kind of in focus.

We see another photo, of Vampire Cat stretching with his butt pointed at the camera. 

[panel 3]

The Other One: You have a lot of these, huh.

We see another photo, this time of Muffin acrobatically pointing her butt at the camera.

[panel 4]

We see The Mother has a whole account called "pics_of_my_cats_(buttholes)" with a lot of blurry pictures of the cats in unfortunate poses.