The phrase "little bulldog" is often used to describe someone who is small and strong-willed, just like a bulldog. It means that this person may be small in size but has a lot of determination and courage. Full definition
The French Bulldog is a sturdy little Bulldog with large, erect, rounded, bat ears, a flat, powerful muzzle and a pug nose. (puppiesndogs.com)
It's time for some puppy love... This cute little Bulldog puppy is sleeping on the couch... He's the cutest puppy ever... I'm wondering what he's dreaming about... That belly looks so soft! (englishbulldogfanclub.com)
Plus, this man can rock a bow tie and they have so many cute options this season (this one has cute little bulldogs on it!). (moretomrse.com)