Wait how long has Bort been outside?
Serious question: Who is Bort? Is it just a fun misspelling? I've heard it over at least a decade and at first thought it was a Simpsons ref but now I'm seeing it in ref to Sesame Street? Idk.
Not sure if this is entirely accurate, but TV Tropes has a line on it:
Brad, Bert's nephew who only appeared a few times in the 70s, is now depicted as Bort, Bert & Ernie's mentally unstable love child.