According to Entertainment Weekly on Tuesday, it seems that actor Benicio Del Toro, who appeared in the post-credit scene in James Gunn's "Guardians of the Galaxy", was unaware that he was being filmed with Howard the Duck. It appears Gunn did this on a lark as an after thought during post-production.
The Collector, played by Del Toro, was the one who informed the Guardians of the origins of the Infinity Stones and his entire museum was laden with Easter eggs from previous films like a Dark Elf from "Thor: The Dark World" and one of the Chitauri as having been seen during The Battle of New York in "The Avengers."
Also, most notably was Adam Warlock's cocoon seen for a second time in The Collectors collection. The first appearance was that of the post-credit scene of "Thor: The Dark World" Lady Sif and Volstagg as they approach Taneleer Tivan with a recent Infinity Stone that they had acquired during their encounter with Malekith.
Gunn still has reason to believe that Del Toro my not yet quite be aware he was in a scene with Howard the Duck. It was actually an attempt to see how far the director could push the content of the film.
“We did not shoot that scene to have Howard the Duck in it. It was something I thought of during post-production. I just thought we’d pushed the movie so far, why not push it all the way for the ending tag?”
The reason of this unawareness was due to the fact that the duck was just plain CGI. He was simply superimposed as Del Toro's only real interaction with a cameo star Fred the dog who plays Cosmo the Russian, telepathic dog. Gunn mentioned that the star has seen the movie a bunch of times, but not since its theatrical release and likely has actually seen the final scene between Howard the Duck and Del Toro.
Even Del Toro mentions he's a bit of a "half-a**" collector himself in an interview a few days ago in a "Guardians of the Galaxy" interview as he tends to start collecting things and then stops collecting after a time. Which after a while, they go into his closet to gather dust.
"Guardians of the Galaxy" are in theaters everywhere and stars "Parks and Recreation's" Chris Pratt, "Star Trek's" Zoe Saldana, "Fast and the Furious'" Vin Diesel, and Bradley Cooper as well.