Noel Fielding and Julian Barratt, the comedians behind the 'The Mighty Boosh', are reported to be speaking to lawyers about getting the ad pulled, according to a story in The Sun.
Hundreds of comments have been left on YouTube and many Brand Republic users have commented on the similarity between the Honey Monster's song and the "crimping" style used in 'The Mighty Boosh'.
One 'Mighty Boosh' fan said: "How dare they steal the crimp! Noel and Julian are the only crimpers in these parts...".
A Brand Republic user commented: "Oh my god... I know we all like 'The Mighty Boosh' but we don't rip it off so blatantly. That really really bad."
"Crimping" is the singing of short, random songs, which has become a trademark of the 'Mighty Boosh' series, featuring in every episode.
The Sugar Puffs ad, created by Bray Leino, marks the return of the Honey Monster character after an absence of five years and features the tagline "Feed the fun".
The ad is set to run until May, and then again from early July to mid-August.
Honey Monster Foods and Bray Leino declined to comment at the time of publishing on the accusations.