 The episode was the first to be storyboarded by Sanchez and Sugar ; Sugar 's previous storyboard partner , Adam Muto , helped clean up the episode 's drawings . Sugar wrote a short rap for the episode , rapped by Andy Milonakis . Originally , Sugar wanted Milonakis to write his own , but he felt the song was of quality and he wanted to rap Sugar 's version . " Hot to the Touch " was seen by 2 @.@ 655 million viewers and marked a significant increase in ratings for the series . It received largely positive critical reviews , with reviewers from both The A.V. Club and Slate applauding the episode 's emotional range . 
