1. Whenever Della Affectionately Calls Her "Penny"
2. While Meant To Mock Her, Penumbra Calls Della "Amazing"
"I thought nothing could stop the amazing Della Duck." - Penumbra
3. Della Got Penumbra "Something Special" That She Knew She'd Like
A training dummy with a picture of Della's face on it.
4. Once She Got To Know Her, Penumbra Realized Della Wasn't So Bad After All
5. Penumbra's Drawing Of Della
Granted, while it was used for target practice, Penumbra's drawing of Della was a pretty good representation of her.
6. Della Was Worried About Penumbra
"You met Penny on the moon?! Is she okay?! I miss her constantly trying to impale me." - Della
7. Della Calls Them A Couple
"We're a classic odd couple." - Della
8. Penumbra Was The Reason That Della Moved Into Tranquility
"But why did you pair her with me?" - Penumbra
"Honestly, it was the only way I could get her to move here. She actually liked you Penumbra." - Lunaris
9. Both Have Similar Objects That Are Meaningful To Them
"We both have spears! That's neat!" - Della
10. Goodbye Hug
Just mere minutes before the Spear of Selene was about to take off, the last thing Della did was hug Penumbra.
11. Penumbra Risking Everything
Penumbra most likely risked her life to try and get a message to Della.
"This is Lt. Penumbra for her friend, Della Duck. All of your defense satellites just went down for some reason. Lunaris is bringing an army to destroy earth. Della, he's coming for your family." - Penumbra
12. Penumbra Saved Della's Life Twice
First time was in "What Ever Happened to Della Duck" when Penumbra shot the moon mite to get it away from Della.
Second time was in "Moonvasion" when Penumbra used the Spear of Selene to destroy Lunaris's ship, saving Della (along with her family).