CooKoo Bird

The CooKoo Bird is a small, blue bird that is a friend of Mario and Luigi on The Super Mario Bros. Super Show!, who lives inside their wall in Mario Brothers Plumbing. The CooKoo Bird rarely appears, and when he does, it's only momentarily, usually to announce the time, alert Mario and Luigi about incoming subway trains from the nearby station, or to just drop the occasional comment.

Toupee
In "Toupee", the CooKoo Bird appeared to warn Mario and Luigi about the incoming subway train, which just so happened to be carrying Inspector Klean, who was on his way over to evaluate Mario Brothers Plumbing, and see if the place was up to code.

No Way to Treat a Queenie
In "No Way to Treat a Queenie", Mario assumed that Luigi had gone cuckoo due to the fact that he was speaking with a British accent. This angered the CooKoo Bird, who popped out of the wall, demanding to be left out of their conversation. At a later point, Mario and Luigi both started speaking with British accents, until the CooKoo Bird returned, yelling at them to stop.

Pizza Crush
In "Pizza Crush", the CooKoo bird would sometimes announce Jodie's arrival when she entered the basement, describing her as a "babe". At one point, when Jodie announced that she would return before leaving, the CooKoo Bird openly wished that he were a plumber.

French
In "French", while Mario was looking for Luigi through the periscope, the CooKoo Bird suggested for him to search in France, as he had been practicing his French skills earlier on. He later appeared after Luigi came back with his new girlfriend, and hinted to Mario that he should learn French for himself to get a beautiful girlfriend like Luigi's.

Santa Claus Is Coming to Flatbush
In "Santa Claus Is Coming to Flatbush", the CooKoo Bird appeared to announce the midnight hour on Christmas Eve, indicating that it was now officially Christmas Day, and wished Mario, Luigi and Nick a Merry Christmas.