This is one of the more humorous moments provided by the Super Sentai franchise, here from Maskman. I still cringe when I see or remember this scene.
Basically, this episode begins with Takeru showing off his mad karate skills, and starts bragging that he's one hell of a model student when he's a kid, good at studies, good at sports and martial arts, he's popular at young age. But then, Igam's most recent plot is to travel back in time and cause time paradox by killing Takeru when he's young.
And when the team meets little Takeru... turns out that he's one hell of a bratty kid who's naughty and obnoxious, flipping Haruka and Momoko's skirts and calling them hags and is overall a loudmouthed brat. Takeru of course gets ashamed at this, but eventually he conversed his little self, motivating him to get better. Eventually as the Maskman returned to the proper timeline, little Takeru gets inspired, and probably he starts getting better...
And back in the present, the rest of the Maskman wastes no time to tease on Takeru for telling them lies about his past. Note on the closeups to each Maskman team when they joke on Takeru, and what kind of face Takeru makes in response. Overall, a very funny episode.