The all-time champion of this remains a story I've told before on the forum. Kristi Markov, wife of Boris, daughter-in-law of Dmitry, was with her husband at a family gathering...and autonomously flirted with her father-in-law; she and Dmitry had a nascent pink bar in their relationship meter.
From the game's point of view, if people aren't related by blood, they're apparently fair game, but flirting with her father-in-law while her husband was right there in the next room? Egad, Kristi, don't you know the Watcher has killed off sims for less than that?
(I didn't kill her off. Boris still loves her.)
As for celebrity tiles, the only malice I've engaged in regarding those came when I had Diego Lobo, who had by that point reached elderhood, go to Del Sol Valley and just rip them right off the walk of fame. He did that for the premade NPC tiles, not for my actual played sims who earned their tiles. You can't sell or trash them from a sim's inventory, but if the sim still has them when they die...well...apparently you can take it with you.