Ho Yay: Mirai and Ryu, to the point they are Mistaken for Gay in episode 24. After Mirai and Ryu (possessed by Yapool) have a stare off, George asks "Don't tell me you two are like that!" When Ryu replies, "Actually, we have a secret we can't tell anyone," George and the others go into shocked hysterics.
When Ryu has a day off, he says to the crew that he doesn't have any plans. They tease him saying that Mirai might ask him out on a date. Mirai kind of did... he did bring Ryu out on a picnic anyways.
Memetic Mutation: Mirai crying a waterfall of tears from his eyes is a common reaction image on the Internet.
How about this, mostly for Ultraman Leo. Schooling the new guy, training him properly, cutting Alien Reflect's sword with his bare hand (and causing his nigh-unbreakable chest armor to flex with a kick), then executing a Leo Kick alongside Mebius with the result you'd expect.
Near the end of the credits of Ultraman Mebius & Ultraman Brothers, we are treated to footage of a party celebrating Ultraman's 40th anniversary. The Showa Ultraman actors are clearly guests of honor but their costars are with them, with clips from their respective series. Near the end of the footage, the actors are presented with bouquets, some by Mirai's actor. Among the guests... all the Ultramen (not just the ones from the movie). Each Ultraman gets a bouquet as well and the actors and silver heroes gather for a photo, but not before a montage with a clip of every Ultraman. It gives warm feelings watching it. A little funny moment occurs because the male party guests are dressed in tuxes... including the Ultramen (although it can't be said they didn't look dapper).
The Scrappy: Mitsuhiko Hirukawa, given his "Every man for himself" jerkass personality, and his lack of hesitation to reveal Mebius' true identity.