Codename: Kids Next Door Season 1 Episode 4

The group catches wind of some ice cream men who refuse to give ice cream to children, so they interrogate them and get the password to their ice cream factory, only to be in for a major surprise from the Delightful Children From Down The Lane, because the ice cream that they take turns into a monster that tries to eat them, but eventually gets defeated by a heater that was turned on by Numbuh 3.