We Wish You a Merry Christmas is a popular secular sixteenth-century English carol from the West Country of England. The origin of this Christmas carol lies in the English tradition where wealthy people of the community gave Christmas treats to the carolers on Christmas Eve such as "figgy puddings" that were very much like modern day Christmas puddings. It is one of the few traditional holiday carols that makes mention of the New Year celebration. The simple chorus and holiday greetings have made it a popular finale to many holiday specials over the years.
The "calculator-slash-Hindi-English-translator" Baljeet mentions may be the one that he gets from Buford (and is automatically smashed by Buford's baseball bat) in "Phineas and Ferb Christmas Vacation!".
Before "A Phineas and Ferb Family Christmas", a music video using a combination of clips from the series combined with some created for the video was aired. It debuted during the opening of the Disney Store in New York City on November 9, 2010. It also aired on Disney Channel November 26 @ 8pm during the premiere of The Suite Life on Deck episode of I'm in the Band. The music video was also seen on Disney XD UK on December 20, 2010. The "Happy Holidays from Phineas and Ferb" scene at the end was cut. The Disney XD logo was seen when the music video played.
The first section of Isabella's line was skipped when it played on Disney Channel.
When Buford sings his lines (and gives Baljeet a wedgie), he and Baljeet are in a Nativity Play; Buford playing as the angel and Baljeet playing as the shepherd (in the Gospel of Luke), who was visited by the angel after Christ was born.
The following lines I warn you, my new -inator/Will force you to serve me later/So why not just choose to cater/To my every whim? and the speaking lines, "Sorry, sir..." from Carl Karl and the talk between Heinz Doofenshmirtz and Francis "Major" Monogram: Oh, great. Well now we've mentioned it. / You know, no one would have noticed if you'd have just kept your mouth shut. were cut from "A Phineas and Ferb Family Christmas".