Howard the Duck and Cosmo

While the Howard the Duck movie was one of the worst Marvel films to date, James Gunn breathed new life into the character in 2014’s GotG. In that film, he was part of the Collector's collection, but he was freed. In the current movie, he showed up early, on the same planet as Sylvester Stallone's Stakar.

Seth Green returned to voice Howard. He'll apparently be back again, as Howard the Duck is set to cameo in future cosmic Marvel movies.

Cosmo the Dog also made an appearance, so to speak. Like Howard, he was part of the Collector's collection in the first movie. In Guardians of the Galaxy Vol. 2, he showed up in a small still that popped up during the credits.

These little things keep the fans watching through the credits.