Back when video stores were a thing, we'd go look every weekend. Because he was bored, my friend starts acting retarded and saying he wants pizza (If you've seen Multiplicity, you know how he said it). I tell him we're not at the pizza store, so we'll pick a movie and then go get some at the Little Caesar's next door. He literally flops to the ground on his back like a toddler and starts screaming that he wants pizza, kicking his legs and flailing his arms. Suddenly, the four other friends that were with us scatter, giggling like little girls, while the entire store is staring at my friend and me. Instead of trying to reason with my apparently retarded little brother, I just tell him that he lost his pizza privileges and grab his arm and drag him out of the store on his back, him screaming that he is going to tell mom the entire time.
We also ordered pizza a lot, before there was shit like delivery fees and driving fees and whatever other bullshit that raises the cost exorbitantly. He loved to act retarded to whomever delivered the pizza. Eventually we got a regular delivery guy, the sweetest little old man that was super patient with the alleged retard. My friend actually started doing his freakout/hyperventilating routine once, and this old man grabbed him and held him so he stopped struggling and told him everything was going to be ok, he just needed to calm down, etc. We felt horrible after that, but he couldn't stop being the retard and let the guy know it was all fake, you know? One time we weren't thinking and my friend was going to pay via check, and the old guy literally helped him write the check, and refused to let him write it for more than the amount of the pizza, thus taking zero tip for himself. If there is a heaven, that guy should be there.
The best one though, was another pizza story. We had a bathroom directly across from the front door of the apartment, so my friend goes in there before they are due and tells me to get the door when it rings. So I open it and see a cute little high school chick standing there with our pizza. Before I can say anything, the bathroom door flies open and my friend comes bursting out in nothing but his tighty whities and chocolate pudding smeared in various places about his body (including his face) with wads of toilet paper stuck to the pudding, screaming in his best Multiplicity voice that he wants pizza. That poor girl almost dropped the pizza right there, and probably peed her pants. I had to bodily tackle him to keep him from getting to her. I mean, obviously he wouldn't have actually done anything to her, but in the moment you just have to act like it is real and play along. If I had immediately started laughing (like all of our friends in the next room that could see us but not the girl), she would have been upset that we were obviously playing a prank on her or something. But you roll with it, like I did, and she is terrified but at least doesn't feel humiliated. And she probably had a fucking fantastic story forever after. We tipped her extremely well at least. She never came back though.
He got me once, and it is completely unexplainable why I cracked at that moment. Maybe because it was so out of the blue. There was a board game store in the mall, and we were walking by and were going to go in, and I saw a really super cute girl working inside. Kinda goth/punk, which I wasn't into at all, but she was still fucking cute as fuck to me despite all that. I made the mistake of mentioning that before we walked in. So we go in, start looking around, and the girl comes up and asks if she can help with anything. Immediately, totally straight face, my friend says, "Do you have the latest Dungeons & Dragons books? My friend here (me) is really excited about the changes they've made to the paladin class." We already knew they didn't carry D&D books there (nor did I ever play a paladin!), and this was mid 90s when it still wasn't exactly cool to play, particularly to tell cute girls that you did. Still, it shouldn't have embarrassed me, but it did, and I could tell just by the heat on my face that I must have turned bright fucking red. I broke the cardinal rule of just going with it and tried to stammer out that he was just messing with me, I didn't even play D&D, but at that point it was beyond salvaging. I, a man in his mid-twenties at that point, just turned and walked out of the store in humiliation. That's the only time, and I have no idea why that got me so bad.