Who had the best guest starts- Disney or Nickelodeon

I wanna believe that most Gen-Z grew up on Disney and Nickelodeon shows, and as I was doing my usual routine of re-watching shows I've watched a million times and ignoring the new to me that I could be watching, I noticed that there were a hell of a lot of celebrity guest stars that appear on both channels, now my question is who had the best guest stars.

This does not include people who were a product of Disney guest staring in a different show, i.e Miley Cyrus, Selena Gomez, Zendaya, Demi Lovato, The Cheetah Girls etc don't count as they are products of Disney channel. 

Disney Channel Guest-stars

• The Suite Life of Zack & Cody had Chris Brown, Jesse McCartney
• The Suite Life of on Deck had Jordan Sparks, Sean Kingston,  Charo,  Dwight Howard, Kevin Love , Deron Williams, and Kurt Warner
• Austin and Ally had Becky G, Dwayne Wade, Leslie David Baker, Maddie Ziegler

Nickelodeon guest stars

• iCarly had The Plain White Tees, One Direction, Michelle Obama
• The Thundermans had MKTO
• The Haunted Hathaways had Rixton
• Cousins for life had Roman Reigns

I know I left a shit ton of shows out but I did this from memory and I have to go do the dishes, I'll edit this as I remember more shows