Morgan weighed in after it was reported that Walliams made unpleasant comments about 'BGT' hopefuls.
The one-off special showcases TV stars' singing skills as they talk about the importance of spending time with others.
Cowell, David Walliams, Alesha Dixon and Amanda Holden were joined by hosts Ant McPartlin and Dec Donnelly at The London Palladium.
Alesha Dixon was eight months pregnant when she was fronting 'The Greatest Dancer' with Jordan Banjo.
The Britain's Got Talent judge says she wants her daughters to be able to see her perform on stage.
Phillips was axed from 'Strictly Come Dancing' in 2009, sparking a huge debate about ageism in TV.
Ashley Banjo channels Elton John by walking out to I'm Still Standing after Diversity's Britain's Got Talent performance sparks more than 15,000 complaints
The 60-year-old broke his back after a bike accident but Alesha Dixon is hoping he will still be a part of 'Britain's Got Talent'.
Arlene Phillips has commented on rumours Strictly Come Dancing will include a same-sex pairing on the next series of the show.