Songs relating to Frisk tend to have heavy Pokémon Mystery Dungeon vibes, with "Your Theme" and "Heart-to-heart" both taking notable inspiration from "Run Away, Fugitives" and "Defend Globe" respectively.
The entire Fort Aquarius section is intended as an homage of sorts to other games, with the battlethemes appearing there being based on Bravely Default, and also throwing in a few sneaking sections for good measure along with Papyrus' "CODAC" and its interface.
Bassiere Von Dohj's first apperance (with the Eyepatch of Power, sleeveless duster, and leggings) takes its inspiration from Beatrix.
Bratty and Catty's new get-up as part of the Guard is clearly based on Yang and Ruby of RWBY respectively, and their themes are clearly based on that of Team Charm.
Mettaton’s first Hotland show (replacing the cooking show) is a blatant parody of Sailor Moon, with Undyne as Tuxedo Mask and “Moonlight Mettaton” dressed as Usagi Tsukino.
During the show, Mettaton ends the fight with Jerry by sending him away in another snowball, specifically one made of snow that's unable to melt in Hotland, so that "YOU'LL NEVER HAVE TO LET IT GO!"
Mettaton’s third Hotland show is a courtroom drama in the style of Ace Attorney, with Frisk as the defendant, Papyrus as their defence attorney, Mettaton as the judge and Undyne as the prosecutor. This segment was released in the format of a sprite animation, not unlike the official comic dub. Even the show title is a Word Salad of all of the Ace Attorney titles.
While fighting the robots possessed by Mad Dummy, Frisk's movements resemble that of classic Mega Man using their phone as a mega-buster. Furthermore, after defeating a robot, Frisk gets a new weapon for this mode that is strong against another one of the robots.
Which is to say nothing of Mad Dummy's standard appearance, which seems a little more...worldly compared to the original.
The first area in The Rift takes it's design cues from Castle Bleck due to the monochrome backdrop, their associations with the end of the world and both dungeons having multiple boss fights before the final showdown.
The fight against the Effigy of Ego plays out quite similarly to YHVH's first phase, in which you have to reject their divinity in order to progress the fight. Much like YHVH, the effigy puts up a facade of kindness designed to hide their hubris and has a Christian theming and whose fights start out with a crowd behind them who disappear as the fight wears on.
The deterioration of illusion Asriel can be considered a dead ringer for the process magical girls undergo during Puella Magi Madoka Magica. As the illusion Asriel deteriorates, they become more mentally unstable and eventually transform into an Eldritch Abomination. The Pawn of Possessiveness is even a Botanical Abomination with a distrustful nature much like Gertrud.
is based on Rick Astley's "Never Gonna Give You Up". That's right, the Inverted Fate soundtrack includes a Rickroll.