Operation Infiltration is the eighteenth episode of Season 6. It aired on April 1, 2015.
Frankie helps chaperone a school field trip that Brick is taking, mainly to try and force some of his classmates to be friends with him. Meanwhile, Mike and his brother Rusty are trying to clean out some of their hoarder-father's junk while he is out of town. While reminiscing in their old bedroom, Mike realizes he picked on Rusty quite a bit when they were younger, and he thinks this may be the reason that Rusty has no ambition in life. Devin Levin tells Axl she loves her siblings and that if Axl didn't she would probably break up with him. He pretends to be cute with Sue when she's around, but he doesn't realize it's April Fools' day.