Examples of celebs getting their favourites:
Craig Kelly don't !et the sun go down on me
Alesha Crazy in love
Steve Backshall use somebody
Peter S mission impossible

o
Kara samba pa ti
Examples of pros getting their requests:
Natalie Lowe King of the swingers
Kevin traditional paso/AT for Susanna/Caroline
Vincent Rumour has it, holiday
Brendan Beautiful day
Pros can also use songs eliminated couples would have used
Celebs can try and change choices (Louisa/russell)
Pros/slebs have tweeted for requests in the past (Natalie/Russell)
Production team have final say
Examples of foisted songs or themes
Tristan mama mia
Ola rock of ages tango (here I go again)
Artem devil in me
Brendan right here waiting
Pasha hungry like the wolf
Pre 2012 Natalie Ian Erin Anton all confirmed they generally chose and 9/10 got what they asked for (unless wanting same track) and often thought of potential tracks/routines re season. But certainly by 2012/3 the pros seem to have been choosing from the best of a bad bunch and being told what themes to do rather than them submitting three choices and the producers picking one pending copyright/repetition/clearance.
Oh and sometimes getting clearance for a song is not as easy as you might think. They could not clear a song in time recently on DWTS until late by which point the pro had gone to the fallback track .
Beyonce Castle reading old threads so you don't have to!

(suffering from insomnia has its downsides) x