Marshall mentions that an accountant in his office is named Matthew Blitz. Matthew Blitz is the name of one of the production staff for this show.
During Barney's description of "The Lorenzo von Matterhorn", he mentions that the move involves several websites boasting the adventures of Lorenzo von Matterhorn. One of the websites' URL is www.tedmosbyisajerk.com and actually exists.
The music featured at the end of "The He's Not Coming" is Mancini's theme from "Romeo and Juliet."
When Lily is talking to Shelley in the staff room at school there is a sign behind her that says 'Please keep the sink clean. Thank you'. This is a reference to the episode Bagpipes in which Marshall tells the group that Lily likes a clean sink.
The fake medical condition that Barney invented for the "Lorenzo von Matterhorn" play is called "phallumegaly", which basically means "abnormally large penis".