From the anime, Omega-Xis getting bored at Geo's school.
Also from the anime, Harp Note distracting Gemini Spark to stop him from killing Rockman...by singing. They (Gemini Spark) spend her entire song staring at her with a dumbfounded look before eventually deciding to ignore her.
In one episode, Omega-Xis possesses a lawnmower to go out for a joyride. The end result is that he somehow ended up crashing into the new EM-telescope Geo had gotten and totally wrecking it. The look on Geo's face when he sees the damage is priceless, with Omega-Xis on his knees and practically begging for forgiveness.
What follows is equally hilarious: Geo then punishes Omega-Xis by making him disguise himself as a D-Pet to enter into a contest to win another telescope. Omega-Xis has a priceless look on his face when he finds out what Geo has in store for him. Not to the mention the "Oh crap!" look he gets beforehand when he hears from Bud about the contest and sees the big grin Geo gets on his face. It's pretty clear Omega-Xis has an idea of what Geo was thinking.
When Omega-Xis is entered, he easily makes it to the finals, but then comes across another D-Pet that is clearly Wolf in disguise, who previously became the pet of a little girl. Although they're obviously different from the other D-Pets and find their appearances suspiciously simiar, they write it off as impossible: Omega-Xis thinks Wolf as too much of a loner to become anyone's pet, and Wolf thinks that Omega-Xis, despite being an enemy, is too much of a proud warrior to put himself into such an embarrasing situation.*
Omega-Xis and Wolf, thinking simultaneously: Even so... They look very alike.
On the note of his habit of taking the lawnmower out for a ride, a later episode shows him going out again, and getting flattened by a steamroller, and desperately calling for Geo to help him out.
The third game has a stage with optional dialogue choices. Boss Battle done, time to save my friends' stuff... they separated! Should I pick Sonia's, Luna's or... BUD's?!
The Humor Program in the Third Game is full of these!
Mega drooling over Hope... Which leads to Geo pulling out a picture of a younger her and him drooling even more... And then Mega questioning EXACTLY WHY HE HAS THIS...
Mega, his usual trolling self, dopes Geo into thinking he can use Meteor G to tell Geo who he'll marry. After Geo angsts in anticipation, Mega finally reveals... Legendary Master Shin! Geo is... not pleased.
The chief of WAZA randomly calling Geo and testing his detective skills by acting like Ms. Tia... Badly.