Well, you could use something unexpected like a splash of cold water or a strong shake. But it depends on the context and the character's personality. Maybe a gentle touch and a soft call would work for a sensitive character.
One way is to provide your own eyewitness account. If you were present when the events in the story occurred, simply stating what you saw or heard can back it up.
By sharing his ramen. In many fanfics, Naruto's love for ramen is a well - known trait. He might offer some ramen to a sad friend, and as they eat together, the simple joy of the food and Naruto's company cheers them up.
You might start by looking in old emails or text messages you exchanged with the person. Libraries or local historical societies could also be helpful. Sometimes, old newspapers or magazines might have covered related events or stories.
Maybe they were just being really creative in a very strange way. They might have thought about the contrast between the relatively 'tame' magic world of Harry Potter and the chaotic and violent nature of Carnage and thought it would be an interesting, if completely off - the - wall, combination.
It could be that the person has a very different view of how fictional works can be related. They might see some very minor similarities in the character development arcs or the idea of a hero's journey in both Harry Potter and Naruto and then take it to an extreme by suggesting such a thing. However, when you look closely at the details of each series, it becomes clear that it's a baseless idea. For example, Harry Potter's journey at Hogwarts is about learning magic and fighting dark wizards, while Naruto's is about becoming a ninja and uniting the ninja villages. They are very different in nature.