In Stargate SG-1 S5E22 "Revelations", Teryl Rothery (Janet Fraiser) voiced the CGI Asgard character Heimdall. Because this CGI character needed to interact with real-world actors, while filming the scene, they got Rothery in a black costume to act as a stand-in who they would later edit out and replace with the CGI Heimdall.

While Rothery is relatively short for a human, she is still much taller than an Asgard like Heimdall. If the other actors in this scene were to make eye contact with Rothery here while filming, after the VFX was added, it would seem as if the characters were looking over Heimdall's head while talking to them. That would look rather unnatural. That is just not how people talk to each other.

So, to make sure that these real-world actors were looking at a height that matched Heimdall's eyeline instead of Rothery's, her blank costume included an image of Heimdall. But this meant that the real-world actors in this scene were delivering their lines while staring Rothery directly in the chest. The cast/crew all found this amusing and had a difficult time getting through the scene because of that.