Barney uses the line "Call me crazy, but child actors were way better back in the 80s". Neil Patrick Harris was a child actor in the 80s, most know for his role in Doogie Howser, M.D. (1989). After reciting his line, a brief clip of the theme song from Doogie Howser plays.
Zachary Gordon, who plays Barney's son "Tyler", made an appearance in season 2 entitled "How Lily Stole Christmas". Gordon played Ted's very religious cousin's son.
Barney mentions his "wife" is a great actress but missed out on a Tony award because it's "very political, it's all who you know." 3 months later Neil Patrick Harris would go on to host the Tonys and won a Tony himself in 2014.
In the beginning bar scene after Barney goes to the bathroom, you can see him in the background, drying his hands on another man's shirt before returning to the table
In season 4 episode 15, when Barney says, "they don't make them (child actors) like they used to", this is in reference to Neil Patrick Harris' role as title character in Doogie Howser M.D.