The comedy, which is currently untitled, stars Christina Applegate as a working mother called Reagan who never expected to have children.
Deadline reports that Pumphrey has joined the cast as Reagan's assistant.
His character is expected to tell Reagan all about the disasters which take place in his romantic life.
Pumphrey previously starred as Calvin in Players. His next project is the movie High Road.
The NBC pilot, which will also star Will Arnett and Maya Rudolph, is being produced by Saturday Night Live showrunner Lorne Michaels.
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