The name of the bar Marshall and Barney enter (which is also the title of this episode) "The Scorpion and the Toad" is a reference to the fable by Aesop ("The Frog and the Scorpion" in the original translation). In the fable a scorpion asks a frog to carry him over a river, promising not to sting him. Halfway across he stings the frog anyway and they both drown, the scorpion saying "it's my nature" - the point being that some creatures (or people) "just can't help being who they are", the motif of this episode.
Barney often uses magic to impress women. Neil Patrick Harris is an amateur magician. Alyson Hannigan who played Lily briefly hosted Penn and Teller: Fool Us a magic themed tv series
First time an episode is directed by someone other than Pamela Fryman. Rob Greenberg directs this episode.