After the classic opening to THE BUGS BUNNY SHOW, the best known opening dance number to an animated series (…as if there were very many to begin with) would be to FAMILY GUY. 

Daffy "died" many times in the cartoons -- but was never replaced in the dance number!
And, in keeping with the (assumed temporary) death of everyone’s favorite philosophically articulate canine, Brian Griffin, even the FAMILY GUY dance number opening was modified to insert “Vinny, the Italian-American Talking Dog” in place of the dear, departed Brian! 


 Oddly, the episode itself had little or nothing to do with Vinny, nor did it mention Brian's death.  Vinny was "just there" as part of the proceedings, which was a typically funny "Peter and Quagmire" affair. 

 I really can’t wait to hear the DVD commentaries, once they cover this period of the series!   
What's "Beyond That Door", Brian?