Barney Rubble from the classic cartoon series The Flintstones can be a bit on the annoying side, but is basically a good and loyal friend to Fred Flintstone, who can be at least an equal pain to him. However, this cannot be said to be true of Barney's counterpart in the long-running series of commercials for the Post Cereals' brand of Fruity, Cocoa and occasional specialty versions of their Pebbles' cereal. In these, Barney is portrayed (humorously) as a stalker, deceiver, and even a corrupter, dragging their pets and children into his schemes to steal Fred's breakfast cereal.
If Fred was ever actually asked to share his cereal (part of the premise is, Barney does this because he won't share), it happened in a very early entry in the series, as most if not all known entries have Barney not even bothering with the request anymore, and seeming to take more of a delight in the schemes and theft than in the actual enjoyment of the cereal. The typical scenario has Barney using a disguise or machine to fool the gullible Fred into handing over the cereal, till the scheme is exposed and an enraged Fred starts chasing Barney to no avail. On rare occasions, Barney will outsmart himself and lose the cereal to another, but as far as is known, Fred never prevails even once. While typical cereal commercial "food-stealing" fare with a sense of comedic sociopathy, this series is likely the only one involving characters widely known outside of the commercials.
In one commercial still shown at least once a year, Fred prepares a bowl to leave out for Santa Claus, whom Barney promptly disguises himself as, only to be exposed by the visit of the real Santa, who urges Fred to calm down and share in the spirit of the Christmas season. Oddly, Santa at no time addresses Barney's attempts at larceny.
The series of commercials (which took over from a more generic series simply showing the Stone-Age families enjoying the cereal) ran from the mid-70's to the late 2000's.
A sketch on Robot Chicken depicted the cereal-stealing efforts leading to Fred's murder, and then a panicked effort at cover-up by Barney.