Ed Helms plays Andy on the show.
EW.com said Collins and Wallace will play Andy's parents and Groban his brother in an episode for the upcoming eighth season of the series.
Groban, who is known more as a recording artist than actor, can currently be seen in "Crazy Stupid Love." The big-screen comedy also stars former "Office" lead Steve Carell, who left the NBC show last spring after seven seasons.
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