Poof makes a cameo appearance near the end of Timmy's dream.
Teenage Timmy sounds similar to teenage Ben Tennyson from the original Ben 10 timeline, who was also voiced by Yuri Lowenthal. Coincidentally, Tara Strong, who voiced Timmy as a kid, also did the kid voice for Ben Tennyson in the original series and the reboot.
Teenage Sanjay sounds similar to Klaus from American Dad, who was also voiced by Dee Bradley Baker, but with an Indian accent.
Teenage Missy sounds similar to Olivia from Family Guy, who was also voiced by Rachael MacFarlane.
Teenage A.J. sounds similar to Baxter Stockman from the 2012 Teenage Mutant Ninja Turtles series, who was also voiced by Phil LaMarr, albeit slightly higher.
Dan Vs. - At one point, Timmy and Ivan guess where Tootie is going to work after graduating High School. Ivan guesses that Tootie is going to work as a cashier at a fast food restaurant, but she thinks of it as unlikely. This is a reference to Hortence, a minor character from the show Dan Vs. who was once the titular character's love interest and a cashier at a fast food restaurant named Burgerphile, and then became a regional manager of the restaurant. Hortence is voiced by the same voice actress as Tootie, Grey Griffin.