Author's note: In the Marvel crossover episode, Buford says "Never get Phineas angry, you won't like him when he's angry." That got me thinking. I'm aware that this is probably inaccurate but, meh.

Edit: Thanks to EpicThoth3 for the constructive criticism. I've made the changes.

Disclaimer: I don't own Phineas and Ferb. If I did, I would have a roller coaster in my backyard and a secret cat agent.

Behind the Flyn-Fletcher residence the gang was gathered under the shade of the towering oak, the half constructed weather-changer buzzing and beeping. Ferb had run in to grab some sodas, so the rest of them were taking a break. All except, of course, the hyper active redhead, who seems unable to stay still longer than a couple of seconds at a time. Said inventor was halfway up the unfinished machine, fiddling with wires. Ferb silently reappeared with five sodas. There was a wide assortment of flavours but the unspoken rule was that the cherry was for Phineas and the grape for Ferb. Unfortunately, there had only been one grape in the fridge, and Buford wanted it as much as Ferb did. Isabella proceeded to begin the pain staking process of trying to get the red headed american to come down and rest a little as the bully made his way over to Ferb.

"Oi, Beanpole! Give that here!" Ferb ignored him. "I said give it!" Buford repeated, the brit popped the cap on the bottle and made a shooing motion with his hand. Buford growled a little. "Are you even listening to me?" Asked the enraged bully. Ferb looked like he wanted to yawn, repeating the shooing motion and turning to see if Isabella had made any progress with his stepbrother, no dice. That was the last straw for Buford, he saw red. Who did this pipsqueak think he was? He made a move towards the other boy.

Poor Ferb had no time to react. The purple refreshment in his hand fell to the ground, mixing with the red blood pouring out of the green haired boy's nose. With a look of almost comical surprise, he slumped to the ground. The British boy had taken the punch full force and it had completely knocked him out. Phineas had chosen this moment to look down from his perch, when he saw his sibling lying bloody on the grass he cried in shock. He jumped down (almost six meters!) to the floor and was running to his brother all in one fluid motion. Now he was closer he could see the smirking Buford, who was glad to have defended his pride.

The redhead growled. It wasn't often Phineas got angry, even less so that he resorted straight to violence, not even when he was attacked by bullies in the school yard or kidnapped by pharmacists who claimed to be evil scientists. However, no one, NO ONE, messes with his stepbrother. He lashed out and hit the larger boy straight in the stomach, his small fists did surprising damage. Baljeet made a move to pull the two apart, however, Isabella stopped him. She knew, not from experience but she had seen it enough, Buford had this coming and they would only be getting in the way. Phineas was usually one to forgive and forget, but when it came to Ferb he was less lenient. She wished the bully luck, he'd need it.

Buford tried to land a hit, but Phineas had an agility most people only dream of. Dodging, ducking and weaving through the barrage of attacks. He struck with surprising power, a result of carrying heavy materials and equipment all day. The impressive strength, married with the incredible accuracy of an experienced builder with practised hands, completely nullified Phineas's small size. Despite Buford's initial advantage, he was not winning.

It went on this way for several minutes until Buford, bruised and out of breath by this point, swallowed his pride and admitted he couldn't continue. Phineas huffed and went over to Ferb, hardly a hair out of place. He sat his brother up and Ferb blinked, ever a man of few words. Phineas started doting over his brother and talking so fast the others thought he would swallow his tongue. Ferb was used to it though and could at least keep up with the endless chatter. Phineas didn't at any point mention the fight to his brother, not for the rest of the day. Buford left early to clean himself up but he had learned something.

Don't make Phineas angry, you won't like him when he's angry.