After Charlie wets his pants, he goes to buy sweatpants with Berta at a swap meet. He asks Berta about the type of store, because he doesn't know what a swap meet is. However, in s01e20, he tells Alan it would be fun to go to the Rose Bowl swap meet and see what they can get for Jake. He obviously knew what a swap meet is in that episode.
Berta tells Charlie that they had shopped at a swap meet.
It was dark when they went to Ronald's house so it is doubtful they went to a swap meet at night since they are usually open during daytime hours.
While Naomi is giving birth on Charlie's couch, her mouth movements do not match up with her screams when she is shown from behind.