The Sin City actress, who also stars with Adam Sandler and Sylvester Stallone in the live-action comedy, said that she only signed up once she heard of Cher's involvement.
"I just look to make a connection with a character in a script, and this one just made me smile. I thought it was super sweet, and when I heard that Cher was doing a voice, I thought, 'I have to be in that!'" Dawson told Hollywood News.
"Sometimes it can be arbitrary which roles I choose, and with this one, it was just the inherent challenge of it."
Dawson added that she enjoyed not taking on a serious role, saying: "I'm a pretty goofy person who can be very demonstrative, so that was great for me to not have to sell every emotion with just a look, being super subtle and burying the context in one line.
"It was about whole scenes, having that much fun where you can really disappear into a moment and have a great time. It was just fantastic to have that many moments in one film."
Dawson split from her boyfriend, French DJ Mathieu Schreyer, of nearly three years in May, as she wanted to focus on her career.
PETA protested the premiere of Zookeeper earlier this week over claims that animals were mistreated during filming.
Watch the trailer for Zookeeper below: