Grownups
Grownups
[Cueball is talking to Megan who is behind a waist-high screen across a doorway with colorful playpen balls behind her.] Cueball: Hey, I was wondering if you had plans for-- holy crap, what happened to your apartment? Megan: I filled it with playpen balls! Cueball: I... what? Why?
[Megan is seen from the front through the door with the colored balls behind her.] Megan: Because we're grown-ups now, and it's our turn to decide what that means.
[Cueball is seen from the side standing next to the open door. Megan cannot be seen, except her hands on the screen, but some of the coloured balls can be seen through the door. A beat panel.]
[Same view but both have entered into the apartment, removing the screen so coloured balls have been spilling out into the corridor. A big pink  love heart drifts out the door.]

Randall is again playing with the child/grownup mental setup. During childhood, adults ("grownups") make most of the decisions and put constraints on what their children do. As children age and eventually become grownups, there are some things that they do not do anymore, as they see them as childish.
Megan has taken these thoughts seriously, and realizes that with her newfound freedom as a grownup, she gets to define what her adulthood means. Free from constraints, she goes ahead and creates a ball pit in her apartment of colored plastic balls. Cueball admires this spirit and enters the ball pit. It is difficult to decipher Randall's true intent behind this somewhat cryptic comic, but it seems from the heart that the two are engaging in sexual activity in the pit.
The trend with adults participating in children's activities is continued in 219: Blanket Fort , and with adults who feel like children while doing adult things as in 616: Lease , which references this comic in the title text.
The title text reveals that Randall also would like to make his own ball pit, but he finds it expensive to buy and also hard to keep clean . Both of these are true - see links. Most public ball pits can easily become very dirty, as many children and toddlers play in them.
[Cueball is talking to Megan who is behind a waist-high screen across a doorway with colorful playpen balls behind her.] Cueball: Hey, I was wondering if you had plans for-- holy crap, what happened to your apartment? Megan: I filled it with playpen balls! Cueball: I... what? Why?
[Megan is seen from the front through the door with the colored balls behind her.] Megan: Because we're grown-ups now, and it's our turn to decide what that means.
[Cueball is seen from the side standing next to the open door. Megan cannot be seen, except her hands on the screen, but some of the coloured balls can be seen through the door. A beat panel.]
[Same view but both have entered into the apartment, removing the screen so coloured balls have been spilling out into the corridor. A big pink  love heart drifts out the door.]
