I think Mr. O in the 1984 series of Spaghetti-Os commercials reminds me of any muppet, but not one specific muppet.
Jim Perry, notable for hosting "Card Sharks" and later "Sale of the Century", bears some resemblence to Guy Smiley. However, I did read somewhere that Guy Smiley was believed to have been modeled after Jim Perry. I was led to believe it was an understatement, since Guy Smiley debuted in the first season of "Sesame Street", until I found out just now that Perry's first game show launched in 1967. I do know that Guy Smiley's original hairstyle looked to be a bit scruffy but in his later years it looked very neat as if he was modeled after Perry.
At the risk of sounding obvious Inspector Gadget and Sherlock Hemlock musta had the same correspondance course in detective work.
Only it was Penny who actually solved the mysteries, and Gadget always got the credit.
I see something with both Sherlock and Gadget. Sherlock was trying to solve mysteries, but the results were something obvious that was overlooked; while Gadget happened to find evidence out of coincidence, or not realizing it is a trap - regardless, it was Penny and her technology who helped solve the mysteries and Gadget always got the credit despite him not doing any work.