Ok In the episode where the Rugrats are scared because Tommy's Aunt (ANT) is coming, it is established that she is a relative of Grandpa. When the Aunt shows up, she looks exactly like Angelica. Angelica is an exact replica of HER mother, yet the Aunt is on Angelica's FATHER's side. How did that Happen?
Angelica isn't an exact replica of her mother, I don't think she looks very similar, sort of, but not that much. she is not an exact replica of the aunt. She could have traits from both sides, and traits of a child don't necessarily come from a direct parent...this isn't a slip-up.
There is no slip-up here. The aunt is actually Tommy's great aunt and she is also Angelica's great aunt. They are related and because of recessive genes they could look very similar.
When people see me with my dad, they think I look exactly like him. But, when I'm with my mom, they say I look just like her. The reason? I, just like every other person in the world, have genetic traits from both my mom and my dad! So, it's extremely likely that Angelica looks very similar to both her mom and her Aunt Mirium.