Will Ferrell’s Son Magnus on John C. Reilly Singing Opera: ‘Amazing’ [Video]

Will Ferrell’s son Magnus has seen his share of wild dinner guests. 

According to Magnus, 20, his dad’s friend John C. Reilly once treated a party to a sweet serenade. In a Lightweights Podcast with Joe Vulpis interview clip newly resurfaced on TikTok, he didn’t hesitate in naming Reilly, 59, as the “craziest person who came over for family dinner.”

“We were doing this Christmas thing where we had close friends and family,” recalled Magnus. “John C. Reilly was there. And it was pretty normal. And then he just at one point started singing opera.”

The Oscar-nominated Chicago star performed an entire aria, he added, laughing. “It was the most amazing thing. Like, it was bizarre! But then you’re like, ‘Wait, this is so funny.’ ”

Will, 57, shares Magnus and two other sons, Mattias and Axel, with Viveca Paulin, his wife since 2000. Reilly, who has starred with Will in multiple comedy …