"Perhaps the first celebrity appearance was in 1928, when Walt Disney himself provided the voice for Steamboat Willie, widely regarded as the breakthrough for animation.
And although there were celebrities in the late 1960s and early 70s who voiced the characters in animated features - think Louis Prima and Phil Harris in The Jungle Book - the gold rush began when Robin Williams took over the role as the big blue genie in Disney's Aladdin.
That was in 1992, the year after Beauty and the Beast became the first animated feature to be nominated for Best Picture at the Academy Awards, and when the modern golden age of cartoons began. Tim Allen and Tom Hanks followed suit in Toy Story, voicing Buzz Lightyear and cowboy Woody; John Goodman and Billy Crystal voiced working-class sidekicks Sulley and Mike in Monsters, Inc.
Besides the cachet of being in a hit film, there's also cash in it for the actors. The three stars of Shrek 2 made $10m each for voicing the roles, according to industry publications.
But Mr Kemp says the reason actors lend their voices to cartoon roles is very much the same as how they decide on their usual roles.
"If Jeffrey Katzenberg is making an animated feature and he calls you up and you're a star, you'll pretty much do it. "It's the same rules that apply to animation that apply to anything else. If the script is good, and the agents want their actors and actresses to be in it, then they will do."