Max Fleischer draws Betty, then leaves her for the night in the studio. Koko escapes from the inkwell and helps himself to a candy bar left behind by Max. He starts to eat some of it but soon gets a terrible toothache. Betty tries to perform some amateur dentistry on Koko, by trying to yank the bad tooth out while dancing. After this fails, she attempts to calm him down but uses too much laughing gas, causing Betty and Koko to laugh hysterically. The laughing gas spreads the room, making a cuckoo clock and a typewriter laugh hysterically. The laughing gas then goes out the window and spreads into town. Both people and inanimate objects begin laughing hysterically, including a mailbox, a parking meter, a bridge, cars and graves. The short ends when Betty and Koko get back in the inkwell and it begins laughing, before panting