When Mainwaring refers to Shakespeare's play in which soldiers "dress up as bushes," he means "Macbeth" in which Malcolm's army cut down branches in Birnam Wood and use them as a disguise to approach Dunsinane Castle.
The episode title hails from BBC Radio's hugely popular comedy series "It's That Man Again", which aired from 1939-49, where it was a a regular catchphrase.
The dog that chases L/Cpl Jones in this episode appears again in the episode Fallen Idol, this time it chases Captain Mainwaring.