It was the sour faced professor Celestia saw that very night.
"Follow me you two," he said, scowling.
They followed him gloomily into his office, which took more like 2 hours to get there.
They entered the office where they saw a chipped desk and a black chair that resembled a bat. The curtains was closed and moth eaten. Candles were lit and were floating, like in the Great Hall, but none had any warmth to them compared to the Hall.
"Sit," he said sternly.
Eerie silence followed them as they sat down on two of the wooden chairs. It was uncomfortable.
"I am a substitute teacher, filling in for Professor Miller, who taught your Potions class," he said bitterly.
Professor Miller was a nice woman, she was also the school nurse who had helped Celestia multiple times in her injuries.
They were looking at him very awkwardly, wondering what was next. He gazed at them for a couple of minutes, then he spoke again.
"So, you will both receive detentions, and lets see... 50 points from Slytherin-"
Squeak.
"I beg your pardon?" His voice raised alarmingly.
"Oh.. Um, hiccups. You know..." Phoenix said unconvincingly.
Squeak, Squeak.
"You are a liar," he said softly, but danger was dancing in his eyes.
Squeak!
The squeak of Akko was louder. Professor Villan was detecting the source of the sound.
Squeak, Squeak!
Celestia nudged her pocket wildly. But the nudge didn't go unnoticed.
"What are you hiding in your pockets? Show them to me, Now!"
Just then, Hagrid came bursting in.
"Hagrid!" Celestia yelled with shock.
"Sorry, Professor Villan. Needed some Flesh-Eating Slug Repellen'. An some- Blimey! What are yeh doin' 'ere Celestia?"
"They were walking around at night. And im suspecting they have an unauthorised pet," he snarled.
"Nonsense! I checked 'em all when we were jus' enterin' Hogwarts!"
"Fine. You're excused."
Hagrid took them back to his cabin to have some late tea.
"Unauthorised pet, eh?" He said smiling gently.
Celestia hesitated, then pulled out Akko. She knew Hagrid's reputation for loving dangerous animals, so what could be so bad about a sweet, cute Niffler?
"Blimey, where'd yeh get 'er?"
"She's wanted. I found her-"
"And rescued her from an old git," mumbled Phoenix.
"In Knockturn Alley."
"The wanted Niffler? Watch out for 'er, she can steal other shiny objects too, ya know," he said.
"She already did! She went into Honeydukes and stole a box of Bertie Bott's Every Flavour Beans!"
Phoenix protested.
"How'd she get in there?" Hagrid said lifting his bucket-sized tea cup to his mouth.
They recounted the whole story back to him feeling more relieved that Professor Villan did not find Akko.
"Well I think I got Slytherins first thing in the mornin' , so yeh can leave 'er 'ere and see 'er in the mornin'."
They agreed with Hagrid, saying they would rather leave her in Hagrid's cabin for the night, unless she would get into more mischief by everyone asleep.

In the morning, they saw Professor Villan inspecting the hump-witched statue. They covered their face with their robes and passed silently by him. As they crossed the vegetable patch to get to Hagrid's cabin, Celestia was wondering whether bringing the Niffler into Higwarts was a good idea. She had already caused so much trouble at one night in Hogwarts! They even broke the law and broke into Honeydukes!

"Righ'. We will be studyin' Nifflers this term. This is a Niffler!" Hagrid showed them Akko.
Celestia smiled as she saw Akko, but still worrying if anyone would realise its her pet. Anyone, as in Jennica. She saw that Akko was peeking from her pocket. Her eyes narrowed, looking at the Niffler.
"Wow!"
"Its so cute!!!"
"I know. I got it from-" Hagrid finished as he saw Celestia and Phoenix's face.
"Er... Found it!"
"You know, she looks mighty like that wanted Niffler, we should hand her in," said Jennica, evilly.
"I got 'er meself. Dont yeh worry bout that," said Hagrid, but his face was reddening.
Suddenly, Akko leapt out of Hagrid's huge arms and jumped onto Jennica's proud face. She was trying to reach out for her silver earrings and scratched her, causing big damage to Jennica's face. Blood was dripping on Akko's claws.
Celestia ran out and grabbed Akko from her. She patted her fondly but still very mad at her. She did not care if Jennica was her greatest enemy, she still got hurt.
Celestia reached out to see if Jennica was okay. She turned her horrified face at her then yelled, "GET AWAY FROM ME! You own that Niffler rat!!! GET YOUR FILTH OFF ME!!!" She threw her arms around violently, and ran off to the castle. Hagrid was trying to remain calm over the class.
Students were looking at Celestia as if she was carrying a disease. She turned around and looked at Phoenix, who's face was horror-struck.