Hergé has a very brief animated cameo almost 13½ minutes in as a blonde man in the carnaval crowd. He can be seen after the scene of Thomson and Thompson's pictures have tomatoes thrown at them in the bottom left of the screen.
Tintin and the Picaros is, chronologically, the final episode of the comic book series, as the last one Hergé completed (the author died before finishing Tintin and Alph-Art). In this animated series, however, it was shown before the Season 3 episode The Seven Crystal Balls: Part 1 (1992), where Alcazar is in exile, making it look like the General has been kicked out of power again.
According to the carnaval sign, part of this episode takes place on either February 22, 23, or 24.