In Japanese, children start by calling their mothers ママ (mama). This is practically the same as English "Mama", along with associated stares of awkwardness and potential social faux pas if a grown man were to use it in public.
Most children will eventually transition to using お母さん (okaa-san, lit. "honored mother"), basically the most common polite way to call one's mother, similar to English "mom" (or "mum" if you're British/Commonwealth). Most will continue to use okaa-san in their adult lives, though some will use a variation like kaa-san (slightly more casual/affectionate, still pretty much the same as "Mom") to okaa-chan and kaa-chan (more casual/affectionate, and far more endearing, similar to "Mommy").
The Kid up there in the comic started off using okaa-san (which I translated as "mom"). He now switches over to おふくろ (ofukuro) This is a term usually reserved for use by older, adult males. Despite the etymology of the word (literally "honored sack"), it is a (casual) term of endearment (not disparaging unlike, say, English "old bag".), making it similar to English "Ma" (and analogous to "Pops" and "Pa", for the other parent), "Mumsy" (British), or "Momma" (African American Vernacular English only, otherwise it might have the opposite effect).
Still, if a boy suddenly switches from okaa-san to ofukuro in front of his mother, well, he's basically declaring he wants to be a grown-up now. For most mothers this will cause a reaction very similar to what Momdroid is experiencing above. And for most older siblings who happen to overhear this—especially older sisters—well, this becomes a field day for endless teasing.
Side note, ofukuro started off as a more respectful/formal term in the Edo era, so if it pops up in a period piece it may have different connotations compared to modern use of the same.
There are also other forms of address. 母 (haha, literally just "mother") is the usual way to refer to one's own mother when speaking to others (who are not your siblings). It's basically the 'humble' equivalent of okaa-san, due to the lack of o-. In polite Japanese speech it's often common to use "humbling" language (kenjougo) when speaking of yourself and subjects pertaining to you, while reserving honorific terms for others. So referring to your own mother as okaa-san to others will sound off, because you're effectively 'elevating' your mother to others.
Of course, referring to other people's mothers as okaa-san is perfectly fine (provided the other party isn't a complete stranger, there is some level of casual-ish acquaintance implied between the two speakers), and is in fact the usual expected way to do so.
There is another term that will pop up—母親 (haha-oya, lit. "mother parent"). This is used to refer to a mother (or mothers) in a formal, impersonal sense—you usually use it when writing a scientific paper or for forms and circulars and the like. (In the broad sense, the word can also be used to refer to any female who had children, including animals.) It is possible to also use it to refer to another person's mother, but the right context can be tricky so it's generally safer to use okaa-san.
In Japanese, children start by calling their mothers ママ (mama). This is practically the same as English "Mama", along with associated stares of awkwardness and potential social faux pas if a grown man were to use it in public.
Most children will eventually transition to using お母さん (okaa-san, lit. "honored mother"), basically the most common polite way to call one's mother, similar to English "mom" (or "mum" if you're British/Commonwealth). Most will continue to use okaa-san in their adult lives, though some will use a variation like kaa-san (slightly more casual/affectionate, still pretty much the same as "Mom") to okaa-chan and kaa-chan (more casual/affectionate, and far more endearing, similar to "Mommy").
The Kid up there in the comic started off using okaa-san (which I translated as "mom"). He now switches over to おふくろ (ofukuro) This is a term usually reserved for use by older, adult males. Despite the etymology of the word (literally "honored sack"), it is a (casual) term of endearment (not disparaging unlike, say, English "old bag".), making it similar to English "Ma" (and analogous to "Pops" and "Pa", for the other parent), "Mumsy" (British), or "Momma" (African American Vernacular English only, otherwise it might have the opposite effect).
Still, if a boy suddenly switches from okaa-san to ofukuro in front of his mother, well, he's basically declaring he wants to be a grown-up now. For most mothers this will cause a reaction very similar to what Momdroid is experiencing above. And for most older siblings who happen to overhear this—especially older sisters—well, this becomes a field day for endless teasing.
Side note, ofukuro started off as a more respectful/formal term in the Edo era, so if it pops up in a period piece it may have different connotations compared to modern use of the same.
There are also other forms of address. 母 (haha, literally just "mother") is the usual way to refer to one's own mother when speaking to others (who are not your siblings). It's basically the 'humble' equivalent of okaa-san, due to the lack of o-. In polite Japanese speech it's often common to use "humbling" language (kenjougo) when speaking of yourself and subjects pertaining to you, while reserving honorific terms for others. So referring to your own mother as okaa-san to others will sound off, because you're effectively 'elevating' your mother to others.
Of course, referring to other people's mothers as okaa-san is perfectly fine (provided the other party isn't a complete stranger, there is some level of casual-ish acquaintance implied between the two speakers), and is in fact the usual expected way to do so.
There is another term that will pop up—母親 (haha-oya, lit. "mother parent"). This is used to refer to a mother (or mothers) in a formal, impersonal sense—you usually use it when writing a scientific paper or for forms and circulars and the like. (In the broad sense, the word can also be used to refer to any female who had children, including animals.) It is possible to also use it to refer to another person's mother, but the right context can be tricky so it's generally safer to use okaa-san.
This was very educational, first lesson of the day and it's only 4 AM.
My kid has entered puberty.
Ma...
I'm home... Mo— Ma.
Switches from okaa-san (polite, most common way to call one's mother) to ofukuro (casual, usually only used by adult males).