I happen to watching White Christmas right now, which is why I’m posting this.
She worked in character roles in movies and TV series (six episodes in this, nine episodes in that) her entire career. She apparently hit the jackpot late in life in the Father Dowling series, but she was well known before that.
I always think of Oliver Platt, though he might be slightly too successful to really fit this, having had a few starring roles over the years. But, generally, he plays a supporting role, and he seems to work a heckuva lot – my wife and I joke that he’s been in 50% of all films made in the past 15 years.
And it’s also great for looking up that person, which makes the former site worthless. Far better would be a search engine where you type what little you know, including looks information, whether a description or similarity to a famous actor.