Ronald McDonald is the happy talented clown mascot of the fast food franchise McDonald's, notably the set of Japanese commercials named "Ronald Rumors". He appears in All Star Smashers as a Stage Hazard on the McDonald's stage. (Where else would he be?) At some points while fighting on the stage, Ronald may occasionally appear and offer burgers to the players before saying "Ran Ran Ru" and leaving. However, there is a possible chance that one of the player's food will morph into a strange worm-like creature with fry-like fangs, causing him/her to painfully spit the creature out, damaging them in the process.
The origin of this hazard comes from the The Frollo Show. In the Frollo Story of episode 17, Ronald takes Frollo to a strange-looking house shaped like a human head, and invites Frollo to sit at the table and eat, producing some McDonald's hamburgers and french fries with another snap of his fingers. After talking to Frollo for a bit about anger, he tells Frollo that greater damage is done when he lets them in, as his food morphs into a strange worm-like creature with fry-like fangs, causing Frollo to painfully spit the creature out.