So it's almost 3:00 AM where I live and I just had the craziest thought: in GoF, when the Weasleys arrive at the Dursleys via Floo Powder to pick up Harry, the twins drop a handful of Ton-Tongue Toffees on purpose hoping that Dudley will eat one. For those who haven't read the books in a while, Ton-Tongue Toffees make your tongue multiply in length,
Dudley, who was on a diet at the time, was naturally drawn to the sweet and picked one up to eat later when his parents weren't watching. Right before Harry left, Dudley did eat the toffee proving the twins' invention successful. Of course, this caused his tongue to start rapidly growing and alarm and, in Harry's case, entertain those around him.
Mr. Weasley knew what caused this reaction and he knew how to fix it. The Dursleys were unwilling to let Mr. Weasley perform magic on their son's tongue until the length finally reached a whopping four feet. This means that Mr. Weasley performed magic (a shrinking charm) in a muggle household where an underage wizard lives. As we know, underage wizards receive a warning for the first time they illegally perform underage magic and face expulsion the second time. Harry had received his first official warning two years prior because of Dobby the House Elf performing a Hover Charm at the Dursleys. Harry took the blame for the magic because he was the only known magical creature at Number 4, Privet Drive meaning that the Ministry thought he was the only one who could perform magic at the time.
This makes me wonder, why didn't Harry receive any warning or letter from the Ministry after Mr. Weasley performed magic? Did it have anything to do with the fact that the Dursleys's fireplaces had been connected to the Floo Network? Did Mr. Weasley sort everything out at the Ministry? Are the Ministry of Magic just complete morons? Let me know in the comments- I need answers!