Sure. A friend of mine once flushed a large wad of chewing gum down the toilet. It clogged it up so badly that the water wouldn't go down at all. He was so embarrassed when he had to tell his parents what he had done. They had to use a plunger for ages before it finally got unclogged.
At a hotel I stayed in, someone must have flushed something inappropriate. The toilet clogged and water started seeping out into the hallway. The hotel staff were running around trying to fix it while the guests were all looking on in amusement. It was quite a sight to see them trying to deal with the mess and the clogged toilet all at once.
There was this time at work when the toilet in the men's restroom got clogged. Turns out, someone had dropped their phone in there by accident while trying to use it and multitask. They didn't want to admit it at first. When the plumber finally retrieved it, it was completely dead. The whole situation was both ridiculous and funny.
Well, maybe draw the toilet as a big monster and the plunger as a sword to slay it. And have the character making all kinds of funny noises and expressions during the battle.
Once during Christmas, my family had a lot of guests. The toilet paper roll in the bathroom ran out while someone was in there. They had to call out for help in a really funny, embarrassed voice. It was quite a laugh when we realized what was going on.
Once, my little brother thought toilet paper rolls were like building blocks. He took a bunch of them and tried to build a tower in the bathroom. It was so funny to see it all tumble down when he reached the third roll.
Once I was in a foreign country using a squat toilet for the first time. I wasn't used to the position and ended up losing my balance a bit while trying to pull my pants down. I nearly toppled over but managed to catch myself just in time. It was so embarrassing yet funny.
Once, my friend went to a very fancy restaurant. When she entered the toilet, she found that the toilet seat had a built - in heater and a music player. She was so surprised and amused that she ended up staying in there a bit longer just to enjoy the 'luxury' toilet experience. It was really funny.
Sure! One time, my little nephew was so excited about his new 'big boy' toilet seat. He ran to it every five minutes, even when he didn't actually need to go. He would sit there, singing songs and making faces at himself in the mirror. Another story is about a friend's kid who thought the toilet was a magical place. He would flush the toilet over and over again, just to watch the water swirl, and then laugh hysterically.
There was this instance where my friend accidentally locked herself in the toilet at a restaurant. She was panicking and trying to get out while we were all laughing outside. Eventually, the staff had to help her out. It was really funny seeing her flustered face when she finally came out.
Sure. Once during Christmas, my family went on a trip. At a small inn, the toilet had a really old - fashioned but cute design. There was a little picture of a reindeer on the wall inside. It made everyone laugh when they saw it. It was a small and funny thing that added a special touch to our holiday.
Yes. I once went into a toilet and found that someone had left a really strange note on the mirror. It said 'If you can read this, you're too close to the mirror'. It made me chuckle.